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Newshound
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The prudent answer is YES and absolutely !

At the same time you pick up a screwdriver or wrench and get ready to perform some work on your trusty Rotax engine, be it a 2 or 4 stroke, you should also be reaching for your engine manual. Let’s face it a manual is as important as your wrench. Your neighbor is not a walking Wikipedia and won’t always provide the correct advice or at least perhaps not in correct sequence.

Even if you think you know, or remember what to do, something unexpected always comes up. What to torque a bolt or nut is a good example. You may need the Line Maintenance manual, the Heavy Maintenance manual or the Parts manual. Another good manual application would be to check if you are required to have a space between certain parts and if so how much space.

This list can go on forever. All smart mechanics and owners will know that the path to easier maintenance and successful engine ownership requires manuals for reference. Even if you are screwdriver challenged and never intend to touch your own engine reading up on the particulars of your engine will help your and the mechanic and you may be able to keep them on a correct path. If your mechanic doesn’t have your engine manuals then have him print them out or you can give him a set for his birthday.

You should source and have on hand all the manuals that apply to your engine. For example the Rotax 912 series engine has 5 manuals that apply to your everyday needs and will answer just about any question that may come up pertaining to that engine.

Many questions right here on the forum can have an answer ascertained from these manuals in a few minutes. I do agree that sometimes there could be a little more information provided or maybe just a little better explanation, but the manuals are an absolute must. The reason you need them all is because information may not be in the book you are using on a specific task. An example of this is the torque settings on many nuts or bolts for a special application. It may have a special torque value that is not the same as another nut or bolt found somewhere else on the engine of the same size. You can buy these manuals or you can print them out right here on the Rotax-Owners Forum.

Purchase a three ring binder and crank up your printer. While you’re at it make sure to print any Service Bulletins, Alerts or Service Information that pertains to your particular engine and keep them on hand as well. I use the manuals all the time in the shop. You just can’t remember everything, besides you need to know when your neighbor’s advice was wrong. These manuals are your Bible, encyclopedia and teacher. You need them to make life easier for yourself and your engine. Follow them and the inspection periods and maintenance schedules will stand a good chance of not having any major issues.

I do realize that engines are mechanical things and do fail so this is another reason the keep your manuals on hand. All engines need maintenance for proper functioning and neglected engines will usually cause the engine owner grief of some sort sooner or later.

Don’t wait for a problem to arise. Read through each manual or table of contents and get some idea of where things are, and read up on how to accomplish a simple procedure. The night before you are going to perform some specific task is a good time to flip open the manual and read up on the procedure.

I know this isn’t a technical article, but I get questions everyday about fairly simple things that are already in the appropriate engine manual. Don’t get me wrong I really don’t mind the calls and I enjoy talking to people from all over the world, but if I can get them to pull up the manual and then point them in the right direction chances are better they will get it right and the next time they will have it right at their fingertips be better equipped to deal with many issues right on the spot… all at home… with that trusty manual.

Manuals: http://www.rotax-owner.com/support/engine-manuals

Service Bulletins: http://www.rotax-owner.com/information/service-bulletins

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Over the last several years I have seen many logbook entries from mechanics, some good, some bad and some just downright ugly. In the last several weeks I have been involved with a buyer looking for a used Flight Design CT ($70K - $90K). This has given me a unique opportunity to really look at logbook entries and documentation (or the lack of it) and see just how that might affect the ultimate selling price of the aircraft itself. Surprisingly, many poor entries have also come from A&P’s and not only RLSM-A’s from the logbook entries I have seen. These poor logbook entries and lack of documentation will cost the owner dearly when it comes time to sell. From what I have seen lately, it’s not hard to lose $5K-$10K in value due to lack of documentation. These are legal records and need to be treated as such. This is one of the only legal ways you can show either someone did something to your plane or did not. As important, log books showing compliance to not only the aircraft manufactures Service Bulletins for the airframe but also for its Rotax engine greatly increases the Aircrafts total value!

One of the first tasks I perform when doing a pre-buy inspection on behalf of a customer is to check the aircrafts Rotax Engine against all published factory Service Bulletins by using the Document Retrieval Service provided on this web site by www.Rotax-Owner.com under the information button on the main page(click here http://www.rotax-owner.com/information/service-bulletins ). This is a FREE Service and worth its weight in gold when cross checking SB compliance of any Rotax engine by serial number. I then cross reference this list to those shown as complied with in the aircraft log books. No records mean no compliance which means extra cost for the buyer if he still wants the plane or a lower selling price for the seller or more often than not no sale at all!

I also use the video section of the Rotax-Owner site (click here http://www.rotax-owner.com/all-videos ) to show both buyer and seller exactly what’s involved in complying with certain SB’s and other tasks I deem required to not only check the condition of the engine(see related videos following this article below) but to also bring the engine up to a serviceable standard. The better the aircraft is maintained and the better the record keeping to show it, the easier it sells and the higher the price it gets! When I was on the Fire Department as a Captain & Medic and doing reports it was essential that everything done be included in that report. I have been to court many times over the years and if it wasn’t in writing it wasn’t done and there is little you can do to save yourself. Cry all you want that it was done, but the jury and judge don’t care. I’ve seen three to four people lose plane sales in the last several weeks due strictly to poor logbook keeping andbad documentation even though the aircraft themselves didn’t look that bad. In the end their aircraft values fell because of it. Paper work documenting the work done is as important as the work itself. How do you know a service bulletin was done, a compression test or a simple carb balance was done? How does the next mechanic know what the other did or didn’t do? How do you know the mechanic found anything wrong or gave additional attention to anything or fixed a problem? If he didn’t log it you may still be flying and it still may be broken and you don’t know it because he didn’t follow the inspection sheets or enter it in the logbook. Not only parts in good condition like hoses etc. may be entered as acceptable but also every deficiency should be entered.

My Mantra;

There is something wrong with every single plane brought in for a 100 hour or the Annual Condition Inspection and it is up to the mechanic to find it.

Show me a logbook entry from a mechanic that says he didn’t find anything and I’ll show you a poor inspection and a very poor logbook entry. I just heard from one A&P and he said he doesn’t log compression test results unless they are under 70 psi residual pressure. WOW! Where is the log that shows any decline or trend when it totally fails the compression test next time? How do you go back and ask him what the numbers were last year. How does he defend a problem that arose in court? You are supposed to use the aircraft Mfg’s and Rotax’s check list. That’s why they went to the trouble to make one up and it is supposed to be part of the legal documentation of that inspection. If you don’t have one for your plane then use the FAA sample or make one up yourself and have the mechanic follow it. You should demand that these check list be followed and signed for your own protection and your pocketbook. You should then keep them with your logbook entries in a safe place and not in your plane. It is your only recourse in case you need legal help because the mechanic did something wrong or didn’t do something he was supposed to do. It will be your legal help with the court system, the FAA and the Insurance Company. When it comes time to sell would you want to buy something that had such poor records thatyou can’t tell what was really done or not done or do you want the plane that has had a serial record of each inspection, oil change, plug change and SB, ext….

You may be getting what you pay for with some mechanics, so if the price is too good to be true maybe you should walk away or at the least ask a lot more question or for references. Like any profession there are good mechanics and bad. Some of the good mechanics have gone through Rotax school and some have gone through the RLSM school. Each one of my clients from day one gets his logbook documented in detail, an original aircraft Mfg’s and a Rotax inspection sheet signed, a separate discrepancy list and all given to the owner/pilot, hole punched for a 3 ring binder. I make notes on the inspection sheets and sign each entry so myself and the owner know I have done the work and I didn’t forget something. If a 100 hour or Annual Condition inspection was done in 4-6 hours you better look for another mechanic. It can’t be done. Those who have hung around while I work know it takes days to complete a proper inspection and the more things you find or the owner has you do the more time you need to add to that. I would say a mechanic that knows his way around a specific aircraft and the Rotax engine and doesn’t have but a couple of minor things to fix may take 2 days for an easy one and maybe more if more problems exist. You are paying good money for your inspection you should get it the way you want it and it should be done.

You should demand that the aircraft Mfg and Rotax inspection check list be followed and signed. The logbook needs to have a lot more than “I found this aircraft to be in a Safe Conditionâ€. Protect yourself and have your mechanic perform to the level of competency you require and deserve.

Here are a couple of examples of what I see on a too regular basis:

This is an entry in the logbook for an Annual Condition inspection minus the A&P’s signature;

1.png

Here is the Annual Condition inspection for a Rotax engine minus the A&P’s signature:

2.png

Some short logbook entries might be barley legal, but they aren’t doing you any good and it’s just lazy not to fill out a proper logbook entry. Paperwork usually takes me 2-3 hours per plane. Just as important have them make entries legible if hand written so anyone can read them. If they can’t, printing them on a computer with a sticky label works wonders.

Here are a couple of examples (and only examples) that are better and your own A&P or RLSM-A may word it differently, many mechanics will list each item on its own separate line, that’s great and makes it easier to follow through, either way this will give you an idea of what a better logbook entry may look like. You need to list all discrepancies and items of importance or any continual ongoing SB’s. By the way the Light Sport Repairman is supposed to sign his title RLSM-A and not any other way for airplanes.

12-12-2011 740.2 hrs. TTSN Maintenance performed on N???? Engine #??????? Aircraft serial # ??????

In accordance with the High Flyer 12 and Rotax maintenance manuals this aircraft had its required Rotax 5 year rubber replacement program, 100 hr. and Annual Condition inspection performed. The engine was removed and re-installed. The engine mounting bolts were torqued to 200 in/lbs as per the High Flyer maint manual. The top right engine mount bolt was bent and it was replaced. Both carb sockets and carb diaphragms replaced. All coolant, fuel and oil hoses were replaced inside the engine compartment and behind the instrument panel. Fire sleeve was placed on all oil and fuel hoses and Oetiker and Band-It band clamps used. The coolant was replaced with Prestone 50/50. An oil purge procedure was performed as per the Rotax maint. manual. Start up oil pressure was 75 psi that settled at 55 psi after the engine operating temp was reached. The carb air intake 3†CEET tubing replaced. The 1 ¾†CEET cabin heat hose on top of the muffler was replaced. Carb throttle and choke Bowden cables were safety wired. The 16 rubber engine isolators were replaced and the bolts torqued to 200 in/lbs per the High Flyer maint manual. Carbs mechanically and pneumatically synced. The magnetic oil plug was checked, it was clean and safety wired. The gearbox friction torque is 424 in/lbs. The plugs were re-gapped at .023 for cold weather and thermal paste applied. Engine run and idle set at 1750 +/- rpm. Both wheels were removed and inspected and both wheel bearings were greased. The front steering pulls right. Lengthened the right steering rod end to push the front wheel slightly left. The ELT test was performed and the batteries are due March 2017. The right center and outer flap bearings were loose. Re-glued with Loctite 480 as per the High Flyer maint. manual. The left lower and the right lower engine ring mount bolts were loose. re-torqued to 29.5 ft/lbs as per the Rotax Heavy maint manual. Compression test results #1 87/86 , #2 87/86 , #3 87/86 , #4 87/86. Gascolator was clean and fuel flow within High Flyer maint. manual specs. Throttle lever friction was too loose. Tightened the friction on the throttle lever to keep it from creeping forward. All engine operating parameters were normal on start up on this aircraft and it was checked for leaks and fluid levels. No abnormalities noted. I certify that this aircraft has been inspected in accordance with the scope and detail of the High Flyer and Rotax maint. manuals and was found to be in a condition for safe operation. This aircraft’s next inspection is due at 840 hours TTSN or by Dec. 31, 2012.

________________________________________________

John Doe RLSM-A LSA Cert. XXXXX issued 5-28-08

----------------------------------------------------------------------------------------------------------------------

Here is a second sample;

10-19-2011 193.4 hrs. TTSN Maintenance performed on N???? Engine serial #??????? Aircraft serial #???????

In accordance with the High Flyer and Rotax maintenance manuals this aircraft was inspected for its 200 hr. and Annual Condition inspection. Gascolator cleaned and fuel flow test conducted / passed. Both carbs removed and inspected per the Rotax maint. manual. Lubed all bell cranks and bearings. ELT test performed and batteries expire March 2016. All hoses in engine compartment are in good condition. The K&N air filter was removed, cleaned and re-oiled. Rotax gearbox friction torque is 428 in/lbs. Carbs pneumatically synced. Engine run and idle set at 1750 +/- rpm. Compression test done for differential: #1- 87/86, #2- 87/86, #3- 87/86, #4- 87/86 psi. New NGK DCPR8E spark plugs were installed, gapped at .025 and heat conducting paste applied. The 4 Rotax engine ring mount bolts were slightly loose. Re-torqued the engine ring mount bolts to 29.5 ft/lbs as per the Rotax Heavy maint. manual. The oil was not due to be changed, but the magnetic plug was inspected and it was clean and safety wired. The muffler joints have a lot of exhaust blow by. Adjusted the muffler to the right 1†to better help align the muffler sockets and lubed with copper anti seize. The underfin rear light was not working and a broken wire was found. Re-soldered the wire and remounted the underfin. The light is now functional. The old factory coolant was drained from the engine and coolant reservoir and Prestone 50-50 was installed. All SB’s are current. I certify that this aircraft has been inspected in accordance with the scope and detail of the High Flyer and Rotax maint. manuals and was found to be in a condition for safe operation. This aircraft’s next inspection is due at 293 hours TTSN or by Oct. 31, 2012.

__________________________________________________

John Doe RLSM-A LSA Cert. # XXXXXXX issued 5-28-08

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Which planes would be more comfortable with, one with the first two log entries or one with the last twoincluding all respective airframe and Rotax checklists in hand? These were only examples and your mechanics wording may be very different, either way there’s no substitute for accurate detaileddocumentation!

I hope this personal reflection on “buyer beware†shows how accurate logbook entries can affect youwhether you’re buying or selling an aircraft .

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I hope this article will prove useful to all my flying friends out there!

Related Videos:

Magnetic Plug Removal and Inspection

Propeller Strike Inspection - 912 / 914

Crankshaft Out of Round Inspection - 912 / 914

Crankshaft Distortion Inspection - 912 / 914

Direct Compression Check

Differential Compression Check

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(Yes it is!)

Another recent incident has prompted me to throw this out for review.

Just wanted to touch bases with everyone concerning our hangar doors. Over the last couple of years too many people have shut their hangar doors on their plane. It is usually the tail and a few wings. That means we are leaving our planes way too close to the door edge whether it be on the inside, but usually these incidents happen when the plane is on the outside of the door.

When I was on the Fire Department there were many door accidents as the truck would pull out. You can imagine what something the size of a fire truck can do to a large garage type door. The cost to the department was hundreds of thousands of dollars. So a policy was written. The door is either 12" off the ground and open for air movement or it was all the way open, nothing in between. The Fire truck was either all the way in the apparatus bay or it was all the way out. No one was allowed to touch the close button until the truck was way out of the station or parked inside. Failure to follow these rules led to a one day suspension and damage to another door or vehicle was much longer.

The point of this is to make everyone take notice that their plane should never be parked half way in or out of the hangar or very close to any door. If it is an electric hangar door it has a certain amount of angle that it protrudes as it opens. These hanger accidents have cost tens of thousands of dollars and I hope this little article helps someone from having this type of accident again. Even if the insurance pays for this incident the repair work and logistics is a royal pain. If I have to have something that crosses the door threshold then I trip the electrical breakers so there is no power to the door and it can't move.

Don't get suspended keep your attention focused and your plane at a safe distance from the hangar door.

From the desk of the Safety Officer

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[h=3]How do you know which one to adjust?[/h]p-2-stk-sync.jpgThe carburetor sync on a 2 stroke or 4 stroke ROTAX Engine is one of the most important functions to keep up with for the health of your engine.

Let’s take a look at performing a carb sync on a 912 series engine. The carb sync is nothing to be afraid of and with a few times at bat, performing this function will become fairly easy. First, why is it so important? The carb sync should be done anytime the carbs or throttle cables are removed or adjusted and at the 100 hour or Annual Condition Inspections. The reason for this is cables stretch, cable hysteresis (cable stickiness), pulley system wear, cables slip and because parts wear and end up with more tolerances. The carbs are almost always out of sync at each 100 hours or the Annual. If you did a carb sync back at the last inspection then they may not be out of sync much, but they will in most cases be out at least a bit. The sync instrument should also be used to set the idle sync if you change idle settings. Let’s start off with thinking of the engine as two engines, a left side and a right side. Two carbs controlling different sides of the engine. You don’t want one side trying to operate at 5000 rpm while the other side is trying to operate at 5100 rpm. These opposing rpms will cause excessive stress and wear on your engine over time and possible damage. You say there is a balance tube in between to help balance them out. The operative word in that sentence is “helpâ€. The balance tube can correct and help with small differences between the two carbs, but it is not a cure all and it is there to help make the system run a little smoother than if there was no connection or correlation between the two carbs...

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So which sync instrument to use? Well that is up to you, but here are a few considerations. You might use an electronic sync instrument like a CarbMate, Syncromate or a set of gauges. Here are a few pros and cons of each sync instrument. The electronic instrument may have the capability to split hairs and give you a very fine adjustment, but they are harder to interpret as far as knowing which carb you want to adjust to achieve a specific goal to bring the two carb vacuums together. It takes more time and going back and forth to get this accuracy. You also need a power supply like your battery to attach electrical leads to operate the instrument. There is nothing wrong with this, it’s just different. The standard type dial gauges (liquid filled are better for dampening with needle valves in line to assist for dampening needle pulsation) allow the user to see immediately which carb he needs to adjust and how much he may need to make this adjustment. This writers’ one thought here is; does the accuracy of an electronic device to split hairs that fine over a gauge really make a difference and can the carbs and engine really tell the difference? If you pay attention to detail and use good gauges you can be very accurate. The drawback to standard gauges is they may not be as accurate as the electronic tools are. Picking one of these sync instruments is strictly up to the end user and their personal preference, both systems are acceptable.

Let’s move on to the actual anatomy of the sync and what to look for. I would like this discussion to be on the use of the gauges because it will offer some visual numbers to work with and helps in the understanding of this article. First the engine should be up to operating temperature. Safety first so put in place wheel chocks, hearing protection, eye protection and a person at the controls for safety. Now you need to separate both carbs. You can use hose pinch pliers to clamp off the rubber hose used to connect the balance tube between the intake manifolds or just remove one side rubber hose off the air intake and plug your gauge into the rubber hose end and the other over the metal nipple it was attached to. Later model engines have two small screws, one on top of each air intake manifold you can attach your sync instruments into also, but you still need to address isolating the carbs by either clamping off or plugging the cross over tube we discussed earlier. This writer prefers to slide the cross over tube rubber hose back off one intake manifold since it makes sure the carbs are fully isolated while preventing any hose pinching damage from using pliers to squeeze the rubber hose instead. This is only what I prefer, it’s up to you to choose your method.

There are two syncs to perform, the mechanical sync and the pneumatic sync. The mechanical sync is really well explained in the Rotax Owners video (http://www.rotax-owner.com/information-reg/elearning-videos-reg/43-exp-si-912-018) and I recommend anyone wanting to perform this task to watch this e-learning video! As well the procedure is also described (although not in quite the same detail) in the Rotax Line Maintenance manual, either way with proper knowledge it’s quick and easy to perform. So now you’re all set in your safety gear so have your safety cockpit operator start the engine. (Don’t forget to advise them that if they see you spin more than three times in the prop to turn the engine off! Also make sure your cockpit manager likes you and don’t use your wife right after an argument with her! smiley-smile.gif)

Now we have the engine running and we take a look at our gauge set. If the needles are pulsating then close the needle valves slightly until they stop and become smooth. Set the RPM to slightly more than idle (off-idle as Rotax calls it). Idle and low RPM is the most critical RPM for smoothness as the power pulses are very pronounced and the gearbox will be working hard as it must settle this argument between the piston power pulses and the huge inertia of the prop. At RPMs over 3000 the engine becomes smoother and the shaking is less pronounced. Let’s mention here that to change the RPMs you adjust the Bowden cable screw either in or out which will add or subtract some rpm. You use the carb idle adjustment stop screw to affect the engine idle only. You do sometimes need to adjust the Bowden cable length to get the idle screw to have enough affect, but we can cross that bridge later.

Okay back to our running engine. Have your cockpit operator advance the throttle up to at least 2000 RPM and check to assure your still in sync, if so continue to advance the throttle all the way up to at least 3500 RPM minimum to assure your high speed sync remains matched. Assuming that’s still working continue to even higher RPM’s just to make sure the carbs remain balanced to the higher power settings respecting the fact you need to assure you are out of the prop blast and the aircraft remains secure. If at the higher RPM’s you don’t remain balanced one of two things might be happening. Because an engine well synced at 2000 RPM should hold that sync all the way to full throttle, if it doesn’t you either have binding in the cables or there is something hanging up in your throttle system not allowing the throttle arms on the carbs to move uniformly with one another. If so; check and correct. The second and much more remote possibility is you have a cylinder that is falling off line due to a hanging up valve or other issue. This is very unlikely on a Rotax but I mention it because even though it rarely happens it might save someone from scratching their heads after verifying the throttle actuation of the cables and throttle levers is all working properly yet an out of sync condition remains. So, backing up to the first off idle sync check at 2000 RPM, let’s say you look at the gauges and see that the left side is at 5†of vacuum (more fuel) and the right side is at 6†of vacuum (less fuel). (Vacuum is expressed in inches of water “H2O or inches of mercury “Hg) The higher the vacuum in our case (6â€), the harder the carb is trying to draw in air and fuel, leaner , less fuel. The lower the vacuum (5â€) the more fuel it is receiving (richer). Keep this in your head about vacuum, the higher number is less fuel (leaner)and the lower the vacuum number, more fuel (richer). Now let’s go to the left side and loosen the Bowden adjustment nuts and screw it back out toward the cable and shorten the cable which pulls the throttle arm and reduces the rpm and fuel flow. Adjust it back until its 5†moves to 6†like the 6†on the right side. Now they should both be equal at 6†of vacuum at 2000RPM allowing you to proceed to the higher RPM checks. If you went to adjust this left side and the adjustment was already way back and you didn’t have enough adjustment there to pull it back any farther then you have two choices. Go to the other side and adjust that Bowden cable adjuster forward to lengthen it and lower the vacuum towards the left side. The other thing you may need to do is shut down the engine, screw the Bowden cable adjustment in towards the half way position and then loosen the cable at the throttle arm screw and shorten it by 1/16†to give you more room to adjust the Bowden cable adjuster farther back on that left side. Sometimes because of how these are setup you may need to adjust one side back a tad and adjust the other side forwards a tad to make them equal and not run out of adjustment on either side.

Now pull the throttle back to idle and see where it is. If you have a 912ULS a good idle is around 1750-1850 rpm to stay above the low RPM vibration and hammering the higher compression of this engine has(it doesn’t like really low idle settings so they should be avoided). Now if your idle is too high after you pulled the throttle back then look at the gauge and see which gauge has the lower vacuum number. Remember the lower the number the more fuel it is receiving. Let’s say the idle rpm is 1900 rpm and you want 1800 rpm. The right carb gauge is at 12†and the left carb is at 11â€. The carb on the left side is getting more fuel and the rpm is too high. So that is the carb we want to reduce the rpm on and raise the vacuum to get to 12†like the right side. So you back out the idle stop screw and the 11†of vacuum raises to 12†of vacuum like the right side. If that made your idle rpm 1800 and you are happy then you’re done. If your idle rpms were still too high then back the idle stop screws out on both sides a little more until the idle rpm is where you want it and the vacuum on both sides is equal. Always double check your work. Run the engine back up to 3500+ rpm and see if the needles are still equal and if not then you may have hysteresis, a broken strand or some other factor causing unequal cable movement that needs attention(or as discussed earlier, that lazy cylinder, another topic for another time). Then back to idle to check that vacuum setting and the idle rpm. If you idle for a long time making an adjustment then run the engine up for a few seconds now and then to help keep it cleared out and from loading up at those low rpms. If your idle rpm was too low (1600 rpm) then screw the idle stop screw in more on the carb with the higher vacuum 12†down to 11†until the vacuum number lowers to match the other side of 11â€and the idle comes up where you want it.

After you have doubled checked your work then shut down the engine and make sure all the jam nuts to the Bowden cable adjuster are snug. Remove the gauge set and connect the carb balance tube setup. Even after a sync the engine may be slightly rougher with the carbs balance tube separated, but should be a little smoother when it is reconnected.

Two last parting comments. The throttle control system in your cockpit at idle should have an idle stop on it and when you pull it back to its stop at idle then the idle stop screw on the carb should just make contact at the same time. If you do not have a throttle stop for idle in the cockpit then you will most likely bend the idle stop levers on the carbs due to the leverage advantage you gain from the cockpit throttle control. This over powering of the idle stops on the carbs will result in the idle ending up too low. This continuous bending towards lower idle could also lead to a much bigger chance of stalling your engine from low rpm in flight and it won’t be when you want it to quit. Pay attention to how your aircraft design addresses this issue and adjust accordingly!

Second; You should check the balance of the carbs at both high rpm and at idle. I have seen some back off the idle stop screw until it no longer functions and that means the carbs can only be synced at the higher rpms and not at idle. That means the engine is operating at idle at opposing rpms. If you thought it was important to sync your carbs at the higher rpms to keep them from opposing each other, reduce vibration and from hammering the engine why on earth would anyone not sync them at idle? This is a poor practice to get into. You spend a lot of time idling. Remember what our Dad’s told us; “If it’s worth doing, it’s worth doing rightâ€.

I know this was a long article, but I thought it may be worth covering for some Rotax owners. If you fell asleep half way through, print it out and take it to the airfield.

FLY SAFE AND FAR AND ABOVE ALL, HAVE FUN LIVING YOUR DREAM OF FLIGHT!

p.s.

Your Rotax engine will give many hours of trouble free operation, just follow the Rotax manuals and provide it with the prescribed on time maintenance. Many of these maintenance topics are covered in greater detail in the video section of the Rotax-Owner web site, click here for a complete list: http://joomla.rotax-owner.com/all-videos

Related E-Learning Videos:

Carburetor Synchronization

Carburetor Balance - 2 Stroke

Bing 54 Carburetor Rebuild - 2 Stroke

Carburetor Needle Position Adjustment

Related Product Review Video:

Product Review - CarbMate

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This happened to me

Taking off from a somewhat short grass strip in northern Wisconsin, two up in my Kitfox, we had just cleared the tree line when my 582 suddenly started to lose power. The only emergency item to try to address this situation is to turn on the Facet fuel pump. Did that and the engine came back to life. Flew home with the Facet pump on all the way. No further problem. Trouble shot the fuel system, filters, lines, carbs, rebuilt the pulse pump, etc. Flew again and encountered the same problem.

I found I could replicate the problem with a full power climb. I could climb for approx 5-7 seconds and then see the EGT's climb about 150 degrees and then fall off as the engine started to die. (This with the Facet fuel pump OFF). With the fuel pump ON, no problem.

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Bing 54 Carburetor Rebuild - 2 Stroke

Carburetor Balance - 2 Stroke

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Carburetor troubleshooting

Rotax Aircraft Engine Manuals

More checking of the fuel system. Even blew string through my lines and pulled a small piece of cloth through them as I was certain I had a fuel blockage problem.

Eventually found that over the course of the 6 years I had flown the plane and done the condition inspections, I always check the hose clamps on the hoses and just give them that little "tweak" to make sure they are still tight.

Well, the pulse line to the fuel pump has a somewhat short nipple on the engine and the hose clamp hung past the end of the nipple just enough that all those little "tweaks" had constricted the I.D of the hose to about half of what it was originally. Still got enough pressure to run the engine O.K. in level flight at reduced power, but not enough for full throttle in a climb.

Replaced the pulse line and all was good again.

Rotax-Owner Addendum:

Rotax recommends the use of gear clamps, Rotax part # 938195 on fuel lines.

Excerpt from the 2 stroke installation manual showing fuel system diagram.

Excerpt from the 2 stroke Illustrated Parts Catalog showing fuel pump and components including the recommended Rotax gear clamps.

This story was submitted by an anonymous user for the purpose of passing on information which might help someone else.

Rotax-Owner has no affiliation with the writer nor takes any responsibility for accuracy or technical content.

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As a recent convert from GA flying, I did a lot of research before eventually deciding to purchase a Tecnam P92 Echo Super with a rotax 912ULS (100hp). One peculiarity of the Tecnam is that it has a tank in each wing, with surplus fuel returned to the left tank, and during my familiarisation training I had been warned that it was possible when flying with full tanks that fuel could be pumped overboard via the left tank overflow.

This could be devastating to your fuel calculations on a long trip. The Tecnam is fitted with a valve for each tank on the relevant door frame, so it is a simple matter to turn off the right tank during post takeoff checks, so that all fuel is drawn from the left until the level is reduced enough to prevent losing fuel overboard.

Related Video: Checking fuel pressure 912, Carburetor Synchronization

Related Technical Articles: Carburetor troubleshooting

I had owned this plane for about three weeks, and decided to travel from my temporary base in Port Macquarie to Horsham via Mildura. On the first leg I departed for Scone with full tanks leaving a nice Fuel buffer in addition to the normal VFR reserves, as I was still convincing myself what normal fuel burn looked like in this aircraft. Being a current PPL, and having a mode C transponder on board, I climbed for 8500ft, as I was heading directly over the Great Dividing Range, real tiger country. I religously performed normal cockpit checks throughout the first 45 minutes, and when the left tank was indicating about 3/4 full reached over to turn the tank back on, and continued with my other routine.

A couple minutes later the noise just stopped without warning, the prop windmilling in the breeze.

Taking a luxurious second to swear loudly, I began slowing to best glide and heading for a landing spot, I had preselected as a part of the normal tiger country routine. The spot I selected was a bit of a clearing on a fairly steep looking slope deep in a valley, hopefully it would be survivable.

As the aircraft had a bit of speed to wash off, I began the first run through the emergency checklist including changing the tank selection as a matter of course. When I completed the checklist for the first time, I focused on retrimming for the glide speed, and just got this set when the engine miraculously sprang back to life, running like a swiss watch.

After circling for a while, within reach of this admittedly dubious landing field (but the best option that was nearby) I got my heart rate back to normal and had a think about what had happened. As you've probably already guessed I had turned the left tank off instead of the right tank on during my routine checks, meaning there was no fuel flow to the engine. Once I had established this was definately what had happened I continued on to Scone for a coffee and a walk around the field, to allow me to appreciate ground that was not looking to kill me, and allow some new found wisdom to sink in.

How do I do things differently now? I have worked out that the fuel cocks point along the door frame when they are turned on, and across the frame when turned off. I also now put my hand on the valve, then pause and cross check before altering the setting, and monitor the fuel pressure instrument for a couple of minutes after touching anything to do with fuel.

What else did I learn? Rushing routine checks is not a smart idea, slow down and do them properly. I had spent time sitting in the aircraft on the ground, after taking delivery, with the Pilot Operating Handbook and hand written all the checklists, doing slight modifications along the way, to improve the logical progression through my specific panel, especially the emergency checks. I then repeated them on the ground until they were committed to muscle memory. This time really paid off when I had to do it for real. The training I have received, both from instructors and myself did kick in automagically, I didn't have to think about it, as it was just a drill, with the pass mark being survival.

Although I only lost about 100ft during this event, in my mind I had a real engine failure, and the emergency checks saved my bacon.

The sound of a smoothly running rotax is a sweet sound indeed these days.

This story was submitted by an anonymous user for the purpose of passing on information which might help someone else. Rotax-Owner has no affiliation with the writer nor takes any responsibility for accuracy or technical content.

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Waterless or 50/50?

Picking a coolant for some can put you on that proverbial fence line and you’re just not sure which way to fall. You need your cooling fluid to prevent high pressure and air or vapor within the system. You need it to transfer heat away from the engine, but it also helps distribute temps more evenly too. Your choices for the most part are a waterless coolant or a mix like 50/50. The waterless coolant most often talked about is Evans NPG (NPG = non-aqueous propylene glycol) waterless coolant (Rotax recommended). Evans NPG is basically non toxic, non-corrosive and can operate at zero pressure. Its boiling point at zero pressure is 375F and the freeze point is -40F and was originally developed with the race car in mind.

Related Technical Article: 912/914 Cooling

Now the next choice is an ethylene or propylene glycol diluted mix. Most store bought brands are 50/50, but some people buy the full strength or non-diluted coolant and then add distilled water to make a mix of 50/50 or a 60/40 mix. The 50/50 mix is good up to approximately 270F with the Rotax 1.2 bar radiator cap. If you have the old .9 bar (13 psi) cap you should replace it with the newer 1.2 bar (18 psi) cap (SB-914-029 & SB-912-043). The freeze point is approximately -34F. Making the coolant with too much anti-freeze (80/20) or too little (20/80) gives you all the wrong characteristics that you want in an engine coolant and can be detrimental to your engine. Having a mix too heavy with anti-freeze can cause loss of cooling and the freeze point will actually start back up. Having too much water and not enough anti-freeze will allow the coolant to heat too high and cause vapor areas within the engine which will also aid in detonation and metal fatigue and not protect well against freezing outside air temps.

So now you think Evans waterless coolant is the best thing since sliced bread. Don’t jump on that horse and race to buy Evans yet. Let’s take a look at the Rotax 912ULS (100 HP) engine as an example. The max oil temp is 266F, the CHT is 275F and the coolant exit temp is 248F. Your coolant temps are usually close to the CHT temps. Rotax has stated in SB-914-029 and SB-912-043 that if you use Evans NPG you can go up to the max temp of 266F, but if you use a 50/50 mix then your max must be lowered to 248F. They did this because the 50/50 mix boiling point of 270F is too close to the 266F max temp. You may get vapor spots within your cooling system and if that were to happen you will lose the cooling in that area and metal fatigue will set in and loss of cooling. If you use Evans to stop a boil over problem while idling then you may have another issue during cruise. Even though Evans has that great boiling point it does have a drawback. Evans does not absorb and distribute heat as well as water. So your temperatures across the board (i.e. oil, CHT’s and coolant) will all be higher by about 25F-30F over the 50/50 mix. If you were already too high in temps then Evans will make it higher. If you have an open air engine that is exposed to the air and not cowed then Evans may work very well for you. If you have a tightly cowed engine then Evans may drive your temps up to red line and negate any benefits you might gain from the boil over protection at idle. For example I tried Evans NPG in my 2006 Flight Design CTSW because it was getting up to 250F+ in the summer. The problem then became that all my high temp alarms were going off on the oil and CHT’s because Evans raised those temps another 30F which put me over the 912ULS max allowable. I drained the Evans and went back to the 50/50 mix and then just unloaded my prop pitch to a little less course and the temps were all fine. If you have an engine heat issue then don’t throw coolant types or dilution strengths at the problem, but fix the cause (i.e. air flow, a lean fuel issue or reduce the prop pitch).

If you use Evans then you must drain and purge the system of all water with Evans Prep fluid which helps remove water from the system. This isn’t hard and is quite easy. Now the other thing to consider with Evans is that if at any time your coolant level is low then you can never add water to the system and must add only Evans NPG and if you are not at your home port that could be a problem.

If you use a 50/50 mix then you can top off with just distilled water. Do not use tap water in your coolant system.

One last comment on coolants, if you use a pure Dex-Cool coolant do not mix any other coolants with it unless it states that it is Dex-Cool compatible and then I would still think twice. Mixing some of these coolants with Dex-Cool can cause thickening of the fluid which will cause several problems. Do yourself a favor and just don’t go there, so pay attention to what you put in your cooling system or what you add to it later.

I hope you now will look at your Rotax cooling system and have a little more information to make that decision on which coolant type is right for you.

Related Technical Article: 912/914 Cooling

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It was one of those wonderful summer evenings you wished would last forever. The air was dead smooth and cooling as the sun moved towards the horizon and not a cloud could be found in the sky. My student and I had done our pre-flight walk around including topping up the fuel tanks in readiness for our one hour training flight. On my way to the airport I had hoped that the 25 gallon portable fuel tank we used to fill our aircraft would have enough fuel in it for our evening training flight. I was relieved to see that one of the other instructors had already filled that tank with a fresh batch of fuel/oil pre-mix as required for our Rotax 503 powered Aircraft. In this case this engine was a pre-mix model with no metering oil injection pump to do that job for you automatically.

Related Videos:

Oil Level Check

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My student had progressed well and was nearing his time for first solo. In preparation for same we had scheduled forced landing practice for this flight to sharpen his skills and ready him for his first solo event. With the walk around complete and our tanks topped off with fresh fuel/oil mix we taxied out for takeoff. As we lined up at the end of the runway I gave my student specific instructions on how I wanted him to proceed which he followed precisely. As expected the aircraft performed well in the cool evening air and the engine hummed a joyful tune as it drove us skyward. As we climbed through 500 feet I asked for control of the aircraft so I could demonstrate an engine out/forced approach procedure. Leveling off I backed off on the throttle to cruise RPM and began to explain to the student exactly what I was about to demonstrate. Then all of a sudden the engine lost RPM and then QUIT! To my alarm I was about to demonstrate the “REAL THINGâ€â€¦â€¦this student was about to get firsthand experience on emergency procedures many only ever hear about!

As I lowered the nose and immediately identified a suitable landing zone I talked through the entire process step by step with the student. All those hundreds of previous simulated engine failures were really paying off now as everything was proceeding as if it were an actual lesson plan. As I Completed my emergency check list and continued to gracefully glide towards our very suitable emergency landing area, I had time to attempt a re-start which I did, the engine immediately came back to life and I aborted our landing approach at a few hundred feet and began a slow turning climb back towards the airport. As we scratched for altitude I again went through the check list, what had I missed? Fuel on both and adequate, ignition on both, temps good what had happened? Just then the engine QUIT AGAIN!!

Again I lowered the nose to maintain airspeed, looked for a suitable landing area and started through the emergency check list, only this time, “THERE WAS NO SUITABLE PLACE TO LANDâ€! Had I just made the worst error in judgment a pilot could ever make giving up a suitable landing area on a “hope and a prayer†the engine quit the first time“BECAUSEâ€???? As we slowly approached the most suitable choice for an emergency landing site available, a plowed field with deep drainage ditches zig zagging across it everywhere, a voice kept running through my head “YOU IDIOTâ€!

As we entered into ground effect I told my student to brace as it was going to be one very rough landing. Fortunately we were in a relatively low inertia aircraft and flew it all the way back to mother earth bleeding off airspeed in the flair resulting in a very slow touchdown speed. Even though we struck several drainage ditches on the roll out, bent both axles and lost a few bungee cords we came out of the event with minimal aircraft damage and no injuries to ourselves (outside of my pride).

After we had a few moments to gather our thoughts(and empty our shorts), our focus turned to “why did the engine quitâ€? The question got answered only a few minutes later as the other instructor came rushing up and immediately admitted he’d forgot to put OIL IN THE GAS! Now there is nothing I appreciate more about a person’s moral character then when one admits they “SCREWED UPâ€, and I will forever appreciate such honesty. It takes real character to admit you made a mistake, many would not!

So what’s the lesson learned? If an engine quits its usually for a reason, and if that reason is not identified through your emergency checklist, and you have a suitable landing area “RIGHT UNDER YOUR NOSE, TAKE ITâ€! It can always be debated what the right decision should have been in this case, but after this experience for me the right answer was much more clear, like the old saying “The most useless thing is air above you and runway behind youâ€, “The most useful thing is the air under you and the runway in front of youâ€! More importantly was how to avoid having to make such a decision to begin with? In our case we implemented new procedures for re-fueling that put proper checks and balances in to“ASSURE†the pre-mix oil always found its way into the gas “BEFORE†it could ever end up in the airplane without it! It doesn’t matter if you fly a two stroke or four stroke, bad fuel is bad fuel, the end result is the same…….pay attention and take nothing for granted!

Happy flying……..

Related Videos:

Oil Level Check

Checking Fuel Pressure - 912 Series

Carburetor Balance - 2 Stroke

General Operation Guidelines - 4 Stroke

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Engine Stumbles on Takeoff!

In my many years of flying I always like to think I’m prepared for a pilots worst nightmare, engine failure on take-off. Until it happens to you, one never knows just how prepared you really are! In this particular case, the engine came back and the pilot made a successful landing, but that momentary sputter really got his heart beating. The real question was, why did the engine stumble, then come back to life?

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Carburetor Needle Position Adjustment

After countless ground runs, the problem repeated itself although again only momentarily. After endless hours of trouble shooting, nothing obvious was found? All the usual places were checked, carbs, fuel supply, ignition system, switches, p-leads what could it be? Eventually, by adding a specially modified float bowl with a sight glass to the two carbs, and after repeated ground runs the engine finally stumbled again and behold, one carb was out of fuel, its float bowl was dry???? After multiple disassemblies, inspections, cleaning, checks and double checks nothing could be found wrong with the suspect carb……we were baffled. Again after multiple ground runs the problem repeated itself and again the float bowl of the suspect carb was dry, what the heck?????

Finally upon closer examination a very small flake of yellow witness paint(Torque Seal) was found stuck to the side of the small fuel chamber directly above the brass needle seat of the Bing Carb. This yellow witness paint(Torque Seal) is used to mark the fuel system banjo bolt fittings on the stainless steel fuel lines as used on a Certified Rotax 912F engine. The purpose is to allow the pilot or maintenance tech a visual reference if the banjo bolt is coming loose. The witness paint is added by maintenance personnel after they correctly torque the fuel system banjo bolts to spec. In this case, during routine maintenance, at some point a banjo bolt marked with the witness paint was removed, and a small flake of the witness paint was allowed to enter the fuel line were it eventually raised havoc! This small flake of paint was just large enough it couldn’t fit into the small fuel inlet hole of the float needle seat, but rather would randomly block off the entrance of this hole shutting off the fuel supply. The small flake remained trapped in the tiny fuel chamber like a lion in a cage just waiting to wreck you day, a nice kitty when stuck to the side of the fuel chamber, a hungry mean cat when stuck over the fuel inlet hole!

What’s the moral of the story, “KEEP IT CLEAN, PAY ATTENTIONâ€, the smallest oversight can have the BIGGEST consequences. In this case, even though a crash was avoided, countless hours of trouble shooting were undertaken at great cost and much anxiety to owner and maintenance personnel, all because of a simple oversight, don’t let this be YOU!

Related Videos:

http://www.rotax-owner.com/information-reg/elearning-videos-reg/270-2_stk_carb_oh

http://www.rotax-owner.com/information-reg/elearning-videos-reg/241-912fuel

http://www.rotax-owner.com/information-reg/elearning-videos-reg/230-regulator

http://www.rotax-owner.com/information-reg/elearning-videos-reg/231-914press

http://www.rotax-owner.com/information-reg/elearning-videos-reg/189-needle

http://www.rotax-owner.com/information-reg/elearning-videos-reg/158-needle

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Let’s talk about the tension on your muffler exhaust springs. Too little?---Too much? Although there several types of exhaust and muffler setups out there, I’ll limit this article to the most common and that is where the exhaust spring holds the exhaust male outlet pipe into the female socket on top of the Rotax stock muffler. If you don’t have a stock Rotax muffler, but do use springs, then this article will still have significance for you.

What happens if there is not enough tension on our exhaust springs? The muffler will have excessive vibration and pulsation from the exhaust and cause the exhaust tube to hammer in its female socket. This will cause cracks, broken out pieces and the chaffing will eat away the edges of the exhaust pipe and socket and too little tension will cause hot exhaust gas leaks that might impinge on your hoses or wiring.

I just performed maintenance on a 912ULS with 375 hours where the female socket on top of the muffler was destroyed from too little spring tension which allowed the exhaust pulsations to hammer on the socket. Since we are talking about this exhaust socket, or joint, I should bring up that this needs periodic lubrication. Use copper anti seize on this joint to help prevent early failure. This is the same anti seize used in the gearbox assembly. (You may have even seen what you thought was brass metal particles in the oil the first time the engine oil was changed. It was, most likely, just this copper anti seize.) When there is too little spring tension the spring hooks will vibrate excessively and wear at the spring hook where it comes in contact with the loop welded on the exhaust tube and muffler. (See attached pictures)

So, let's examine the solutions There are a few different types of springs available not to mention all the ones owners may buy at the local hardware store. I recommend springs approved by Rotax. So it may be hard to get the perfect tension addressed in this article so again, I will limit this discussion to just two types. (Pictures below are the two most common.) One is the Rotax spring part number, 938-795. The other one commonly seen is a stainless steel spring and is much heavier in construction. It isn't necessarily better, just different and the correct tension will prevent premature wear. The wrong tension can make any spring wear out or break in as little as 200 hours. If you use the heavy stainless steel spring an effective quick evaluation for the best tension is obtained when you can see a little daylight between the coils or you have enough room to insert your fingernail between coils easily. If you can't see any space, then the spring may not have enough tension. At least you will know that there is some tension on the spring if you see a little daylight and it won't be over stretched. The correct calculation, following Rotax’s maximum 10mm(.4â€) stretch would be calculated as follows: Each spring has approx. 11 coils but the first coil is zero leaving 10 potential spring gaps. If you have ten spaces between coils, and maximum stretch is 10mm(.4â€), your maximum allowed distance between coils is 1mm(0.039â€). Let’s call it 0.040†and use a feeler gauge to measure it, straight forward, simple!

Get back in your seats; we aren’t finished yet. We need to apply some high temperature RTV silicone. This helps prevent vibration from wearing on the spring and helps give it a little extra support. There are two ways to apply the RTV silicone. The least common and least desirable way is to fill the spring’s interior with the silicone. I don’t particularly like this because you need to safety-wire the spring and remove it at times and then it becomes a problem trying to get all the RTV out. The best, and most common way, is to lay a bead of the silicone from top to bottom on the outside of the spring. Here is where it was important to see a little daylight between coils because you want to work the silicone in between the coils as you apply your bead down the side. The bead should be at least 3/8â€- 1/2 inch wide and 3/16†– 1/4 inches tall. This gives the silicone some body and strength. Applying a pencil thin bead, or a line down a fully collapsed shut spring is close to worthless.

One last thing you should do is safety-wire those springs. Too many have gone through props on pushers. You can run the wire down through the center from welded loop to loop, or through the spring and back around the outside, but still through the welded loops. Do not make the safety wire tight. Leave a little play in it so it can move. It isn’t there to hold the exhaust together, but only keep the spring in place in case it comes off or breaks. If you make the wire tight the vibration will just wear through the wire quickly. My personal choice is to use .041 wire and not .032.

I have attached a couple of pictures to show what excessive wear will do to a heavy, stainless steel spring hook and a muffler socket. The red RTV silicone was applied well, but isn’t between the coils. There is a picture of the Rotax spring connected to the exhaust with the RTV silicone and safety wire already applied.

thumb_1.jpgthumb_2.jpgthumb_4.jpgthumb_3.jpg

For readers reference I’ve attached page 43 of the Rotax installation Manual which states Rotax’s official technical position on proper muffler spring tension.

pdf_small.gif 67.35 Kb Exhaust Installation as per Rotax

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Keeping it simple and effective for the common setup

Let's discuss prop pitch and how it affects flight characteristics. It can help flight characteristics or it can hinder. I'm often asked; What's the correct prop pitch for a specific plane? There is no single answer as many props are available to us today for Rotax engines and for different fuselages. There are, however, some commonalities and that is where we are headed in this article.

Certain principles do apply in either the 2 stroke or 4 stroke engines, although the numbers will be different, as with most ground adjustable props. This article won't get into all the designs, blade twists, angles, thrusts, shaft powers, etc...etc. Whoa, just thinking about it puts my brain in a tail-spin. We are going to keep it simple and easy to follow. I am going to use the Rotax 912ULS as an example.

Related Videos: Propeller Strike Inspection | Crankshaft Out Of Round Inspection | Crankshaft Distortion Inspection | Preventing Detonation - 4 Stroke

First let's pick a few numbers to keep in the back of our minds for later. We are going to shoot for certain idle rpm, so let's pick 1800 +/- rpm and 5500 + rpm for wide open throttle (WOT), flat and level at your average cruise altitude. It wouldn't make sense to set a prop for sea level when you are at 8,000' msl all the time. Why 5500 rpm as a target? That is the "continuous run" rpm Rotax recommends for the Rotax 912ULS and that rpm can be flown all the time if you chose to do so. Another good reason would be if you were to break a cable or had a throttle control failure. One carb would probably go wide open, as it's supposed to do and then you could advance your throttle and have the other carb go wide open. You could then fly to wherever you needed for hours; shut down and land. Anything over 5500 rpm (i.e. 5600-5800 rpm) would limit you to a 5 minute run time. This is just a little benefit for the 5500 target rpm, but not a determining factor. A prop manufacturer will usually have some instructions for their prop and sometimes a suggested starting point for pitch depending on the engine. Another often asked question is, What should my static rpm be? There is no specific or accurate answer for everyone's engine and prop. The static won't mean much if you only want to fine tune your existing setup. Static is more important for the first run owners or for new prop installation. The static rpm setting is just to get you in the ballpark and then you will need to fine tune it for your specific aircraft while flying WOT at your average altitude. So keeping it simple, you will want to set the pitch on most props to achieve a target with a beginning static (ground run) WOT rpm of around 4950-5100 rpm, but your static rpm may be slightly different depending on what you wanted for a final in flight WOT rpm outcome.

(Note: These next figures are general and yours may vary slightly) To do this properly, you will need to go fly at your average cruise altitude and fly flat and level at WOT for at least 1 minute. Now if your WOT rpm at this time is 5500 rpm and up to 5600 rpm you're probably set up fairly well for your engine, temperatures and fuel economy. If you are up at 5700+ rpm (150-200 rpm which could be high for your circumstances) then you may want to land and add a little pitch (about 1 - 1.25 degrees) back into the prop pitch, which will make it more coarse.

If you already have your prop setup is only turning 5200 rpm WOT flat and level you need to flatten or reduce the pitch approximately 2 degrees to achieve 5500+ rpm. Now you may have some special circumstance like a float equipped aircraft (heavy aircraft) that needs a little better climb, so a climb pitch of 5600-5675 rpm WOT might be warranted. We need to tune our props for the type of flying that we do.

[h=4]What else does my prop pitch do for me?[/h]Setting the prop pitch excessively coarse (i.e. 5000-5200 rpm WOT) causes excessive stress on engine components and gearbox which may necessitate early maintenance. Having the pitch too coarse will cause higher engine (CHT, EGT) and oil temperatures, excessive fuel consumption, poor climb and decreased cruise speed. Your engine doesn't have the horse power and torque to turn an excessively pitched prop. All piston engines have their limits and the props all have limits, too. So if your engine temps are up and your WOT engine rpm is below 5500 rpm try unloading the engine by reducing the prop pitch. If you have a prop that is too flat then it may climb well, but have a loss in cruise speed and of course engine temps and fuel are affected again.

Your exact numbers may vary some, but you now have a general idea on what to look for and how it may affect your flying and engine. We'll keep this discussion on the root topic of ground adjustable props. Special circumstance rpm settings and constant speed props will warrant discussion in a future article.

One last parting comment: If adjusting prop pitch sounds complicated, it isn't; it usually will only take 30-40 minutes, a couple of wrenches, a prop protractor and/or a level. So take the time to fine tune, your engine will say thank you in improved performance.

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[h=3]What each Rotax 912 owner should consider[/h]New, Rotax 912 series engine owners invariably ask what oil should be used. There is no perfect oil and that can make this discussion an arbitrary topic. Many owners just ask their neighbor what oil to use, some call their aircraft Mfg., all should consult the Rotax Suitable Operating Fluid publication SI 912-016 (latest revision) as not all oils are created equal. In this article we will take a look at a few oil traits and additives.

Related Videos: Fluctuating Oil Pressure | Purging of the Lubrication System | Oil change procedure

It is out of this writer’s and Rotax’s scope to possibly test or comment on all the oils on the market. It is not this writer’s position to have you purchase any certain brand of oil, but only to help you understand what’s in an oil and why we need to use a good motorcycle oil in the Rotax 912 series engine for its longevity and health. I have attached an oil study comparison by an independent tester commissioned by Amsoil dated March 2006 and written by David Leitten and I want to give him credit right up front. This is a very good article and you will walk away with a much better understanding of oil additives. My article will parallel and summarize his article to make it easier to follow. His article goes a long way in having you understand why motorcycle oil is different than car oil and what additives are important to you and your Rotax 912 engine. You will need to draw your own conclusions as to the oil that you want to use, but now you will be well armed with good information. Oil tests are usually conducted under the American Society of Testing Materials (ASTM) standards. Rotax highly recommends the use of motorcycle oils and here are just a few reasons. (Note: When I use the term motorcycle it is applicable to the Rotax 912 as a reference)

[h=3]The difference[/h] Here are a few reasons we do not want to use auto oil in our Rotax 912. Our engine speeds (RPM) are much higher as is compression (10.5:1 for the 912ULS), The horsepower ratio is much higher, and as also engine temperatures. The one really big difference between the auto and the Rotax 912 is the Rotax shares its engine oil with the gearbox, where an auto engine has separate fluids for these functions. This item is a big concern when choosing motorcycle oil over auto oil, as the properties need to be very different. We do not use our aircraft as often as our cars so those extended down times cause problems such as rusting and acidity. The attached article delves more deeply into these subjects.[h=3]Oil Properties[/h]Viscosityis a measure of an oils thickness and it helps protect the engine as oil is non compressible. If your oil is too thin it can be pressed out of the way where the metal surfaces come into contact. Some oils do not keep their viscosity rating under high workloads and shear and you could lose some of the viscosity protection. An oil that is too thick causes excessive work and temperatures for the engine and could cause some problems on a cold morning start up.

Shear protection is a measure of an oils capacity to thin out or reduce its load-carrying capacity. The Rotax 912 operates at higher rpm temperatures than an auto and the gearbox shares the engine oil. This high mechanical rpm, higher engine temperatures and close tolerance operation can cause some oils to thin out and not protect your engine as well as some other oils with higher shear properties.

ZDDP (Zinc Dialkyl-Dithio-Phosphate) WOW that’s a big word. This is a zinc phosphorus compound. This is a very important additive for us compared to an auto. This additive was very important in older autos as a protection against metal surfaces coming into contact. You see, for most of the last century, the almost universal method to open and close engine valves was via flat tappets (solid or hydraulic lifters if you will) (like the Rotax 912), and the ZDDP additive was there to prevent or reduce wear between the lifters and the camshaft. The ZDDP in the minute amounts of oil that will get burned and exit through the exhaust system which will shorten the life of catalytic converters. Thus the EPA mandate to eliminate ZDDP from engine oil. The auto makers have responded by designing engines that utilize roller lifters or overhead camshafts, and have no need for the protection offered by ZDDP. The older auto owners can still purchase this additive from automotive stores. This additive was reduced to around 800 ppm. It coats the metal surfaces and when they come into contact acts like a sacrificial surface. Zinc is not the most important additive here, but the zinc phosphorus combination is.

The 4 ball wear test. This is test to see if the oil can protect parts from metal to metal contact and is spelled out very well in the attached article. Zinc levels in this test seem to play a big part in an oils ability to prevent metal to metal contact.

Gear performance test is a measure of an oil’s viscosity and how additives contribute to gear protection under extreme pressure, shock, sliding and shearing forces. This is very important to the Rotax 912 gearbox. If you have ever taken a gearbox apart for an inspection you can see the gear wear from the use of certain oils and the absence of wear with good oil.

Oxidation test is a test to see how well oil holds up under heat. If the oil starts to break down from heat it will cause oxidation to occur which shortens the life of the oil and causes more carbon accumulation. Increased levels of ZDDP help prevent oxidation.

Volatility: a.k.a. Evaporation of some of the oil components causes higher oil consumption and higher viscosity. High temperature is the main cause of this problem.

Oil Acidity: Oil base stocks, but mainly their detergent additives are designed to help reduce the amount of acid build up.

Foaming: This has been an ugly word in the early days with some of our oils and it was enough of a concern amongst other reasons that Rotax, several years back (SB-912-040 R1 dated 8-2003), increased the volume of oil in our oil tank to help combat this problem. Some oils are certainly up to the task more than others. Foaming is caused because of our gearbox and engine oil combination. Foam as we know has air bubbles and this prevents the oil from protecting our metal to metal surfaces. Foaming causes increased wear and oxidation. (Note: Your oil tank dip stick should have a squared top where you grab it. The old dip stick is round.)

Rust Protection: Many of us live in humid climates and moisture in our oil and on internal parts is inevitable. This of course is one reason Rotax wants you to obtain at least 212F oil temperature to boil off any moisture. Oil does not protect or prevent rust, and inhibitors to the oil must be added. Letting an engine set for extended down times allows rust to cause pitting on metal surfaces and in our bearings. If you are unable to fly for extended periods it is better to at least start the engine and let it run at operating temperatures for a while on the ground.

To add to your reading it should be noted that the base stock oil is just as important as any additive. Without a good base stock then the additives may not help much. You should be using a full synthetic or a semi synthetic oil and not using a straight mineral based oil. The straight mineral based oil will not provide the protection from all the items we have talked about above. It lacks tenacity and robustness against everything that wants to damage the metal parts in our high performance engine. If you use auto fuel then you can use the full or semi synthetic oil and if you use 100LL use only the semi synthetic. The full synthetic with 100LL can’t suspend the lead and it tends to fall out of solution and settle in places we don’t want it to.

[h=3]The bottom line[/h]Here are a few oil stand outs and this of course is not all inclusive because not all oils around the world can be tested for our purposes. You need to make up your own mind in choosing an oil that is right for you following references made in Operating Fluid publication SI 912-016 (latest revision) as the following is just the opinion of this writer and IRMT mechanic. These following oils have shown good characteristics in lab test and field use. These are all motorcycle oils.

Full Synthetic: (not in any order) Use with auto fuel only.

Mobile One Racing 4T 10-40W,

Mobile 1 V-Twin 20-50W,

Amsoil 10-40W or 20-50W

Semi Synthetic:

Aero Shell Sport Plus 4 10-40W,

Golden Spectro 4 10-40W or 20-50W

From all the research I have done, these oils contain good, high quality base stock oils and sufficient additives to support the engine.

Side Note: I wanted to mention something I have heard and researched. Aero Shell Sport Plus 4 was designed and is mfg. in England. Some oils are mfg. in different geographic locations and sometimes that changes their properties. So a one location mfg is a good thing. I understand that Aero Shell according to the Aero Shell Sport Plus 4 MSDS sheet has .1%-.2% of ZDDP which translates out to 1000ppm - 2000ppm.

I hope after reading these two articles that you will look at your Rotax 912 oil a bit more critically and evaluate whether you have a good oil or maybe make a change. But either way you now have more information to make that important decision.

pdf_small.gif Oil-Comparison 2.01 Mb

Related Videos: Fluctuating Oil Pressure | Purging of the Lubrication System | Oil change procedure

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sp2.jpgThere is a right and wrong way to install spark plugs on your Rotax 912 series engine.

First, we need to use the proper plug, so make sure you have the proper numbered plug. Don’t take it for granted they are all the same, stop and look at each one. It’s imperative that they are uniformly identical in the number. Using the wrong plugs will, inevitably lead to problems, so be alert.

For example, the 912UL (80 hp) uses an NGK DCPR7E and the 912ULS (100 hp) uses the NGK DCPR8E. The correct gap for these is .023 - .027. The packaged plugs will usually have a wider gap and will need to be re-gapped. It’s better for you run a wider gap during the summer, and the smaller gap during the colder winter, your starts and over-all running will be better.

Related Videos: Preventing Detonation

Now here is an important point and I see many mechanics and/or owners get it wrong, especially those who have not attended a Rotax school.

DO NOT APPLY ANTI SEIZE to the plug threads!

You should be using a thermal conducting paste which can be purchased from any Rotax distributor. Other aircraft engines do use anti-seize, but Rotax does not. As a matter of fact, I have many GA owners now using this thermal conducting paste over anti-seize. Anti-Seize did its tour of duty, but the new technology dictates that it’s time to move on. The paste will help with any galling issues that sometimes happen when you install a dry plug. Do not install the plugs dry (except for the 2 strokes). This is a silicone based white paste which is also used in the electrical contact industry. Apply the heat conducting paste to the top 2/3 of the plug. Do not get this on the electrode because it will not burn off and cause the plug to misfire. When applying the paste there is no need to glob it on. In this case just enough trumps too much. I use my small finger with just a dab on the tip and rotate the plug to spread it on the threads evenly.

The plugs now can be installed and torqued to 177 in/lbs (14.7 ft/lbs). Now this is a point, but one that is too often overlooked, so stay focused. It’s all too common to find loose plugs simply because someone got sidetracked and forgot to tighten them.

The following picture shows what they may look like. The top plug was torqued in place and the bottom one was loose which caused bypass gases and fuel blowing past the threads.

Make sure you push the spark plug cap back in place correctly and hear that unmistakable ratcheting sound as it slides down over the terminal end.

Side note: If a plug starts to bind or become hard to thread, STOP. Remove the plug and run a thread chase down the threads to clean them out. Forcing a plug when it is hard to turn will only damage the plug threads in the head. They make an inexpensive, special tool just for this and you’d be wise to have one in your tool kit.

[h=3]What is my plug telling me?[/h]Much will be learned about your Rotax engine condition, as well as how it is running, by properly reading and "understanding" your spark plugs.

This page will show you pictures, as well as explanations on cause and effect of what you see when inspecting your spark plugs.

Look at the spark plug porcelain for the color and condition. Plug colors can tell you how the engine is running and obviously, that can be very important.

Plugs change color and the different colors can indicate such things as engine overheating or if the engine is worn. The color can be ascertained by looking at the porcelain insulator and then by comparing to the plugs shown in the next few pictures.

[TABLE=width: 97%]

[TR]

[TD=width: 109]sp1.jpg[/TD]

[TD=width: 480]A tan colored plug means that the engine is running normally and the air/fuel mixture is correct. This is the correct color a spark plug should be and it tells you everything is fine with the engine. This plug shows normal wear in the center electrode. A new plug will have square edges that help the plug fire more efficiently.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp2.jpg[/TD]

[TD]This plug is worn out from being used for a long period of time. Notice how the center electrode is round and worn from use. A spark plug that is worn takes a lot more voltage to fire and can cause poor engine running.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp3.jpg[/TD]

[TD]This plug shows what can happen when something hits the spark plug from inside the engine. This problem must be repaired before running the engine further. Make sure the spark plug is the correct length for the engine.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp4.jpg[/TD]

[TD]Excessive detonation has caused the porcelain on this plug to break away. If this engine is allowed to run, engine damage can occur. Make sure the fuel octane is high enough for the engines requirements.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp5.jpg[/TD]

[TD]A white colored plug is caused by engine overheating. Failure to repair this engine will result in severe engine damage. Common causes for this are: Incorrect spark plug (heat range too high). Low octane fuel. Timing is not set properly. Cooling problems, (dirty cylinder fins; no, or low, water on a water-cooled engine; low or no engine oil). Carburetor air/fuel mixture is too lean (too much air). Leaking crankshaft seals. No oil. Base or head gasket leaks, or crankcase leaks on two stroke engines.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp6.jpg[/TD]

[TD]This plug has ash deposits which are light brownish deposits that are encrusted to the ground and/or center electrode. This situation is caused by the type of oil used and by using a fuel additive. This condition will cause a misfire. This can be also caused by changing oils in midstream.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp7.jpg[/TD]

[TD]This plug is oiled fouled, caused by poor oil control.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp8.jpg[/TD]

[TD]Pre-ignition will usually appear to have a melted center electrode and/or ground electrode. Check for incorrect heat range plug, over advanced timing, lean fuel mixtures or even hot spots or deposit accumulation inside the combustion chamber.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp9.jpg[/TD]

[TD]Sustained Pre-ignition, which will usually look as a melted or missing center electrode and/or ground electrode as well as a destroyed insulator. Check for incorrect heat range plug, over- advanced timing, lean fuel mixtures or even hot spots or deposit accumulation inside the combustion chamber.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp10.jpg[/TD]

[TD]Splashed deposits look as if they are small islands of contaminants on the insulator. This is usually caused by dirty carburetor bores or air intake.

[/TD]

[/TR]

[TR]

[TD=width: 109]sp11.jpg[/TD]

[TD]A black dry fluffy colored plug is caused by deposits from a carburetor that is running too rich (too much gas), or excessive idling on some engines. Black smoke coming from the exhaust is a sign of a rich air/fuel mixture. The rich air/fuel mixture must be repaired before installing a new spark plug. Common causes for a rich air/fuel mixture are: A dirty air filter, The air mixture screw or carburetor needs adjusting, The choke is sticking, or the carburetor float height is out of adjustment or float is sticking open.

[/TD]

[/TR]

[/TABLE]

Here is a good reference:

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

[h=3]Understanding the numbers on my spark plug?[/h]numbers.jpg

Related Videos: Preventing Detonation

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Rotax has a new addition to their parts inventory: the new Rotax oil filter. It’s manufactured by Mahle, part #825-010 (012) and made in Austria. Rotax took a look at all the different engine installations and I believe they thought it was time for a change and a change for the better it was. The new oil filter comes in an all white box verses the old filter box that was blue/white.

Related Videos are: Oil Filter Installation, Oil Change Procedure, Oil Level Check

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It is slightly longer by 3.5mm or .138 in., but this is not where the changes stop by any means. Some changes were sweeping. For instance, some are specifically designed with the mounting of the oil tank in mind. This is important because we have a dry sump system and not a wet sump system . The white silicone drain-back preventer (valve) is improved with little or no oil being allowed to drain out of the filter while the engine just sits. This was designed for engine setups where the oil tank is mounted a bit too low, which prevents the oil from draining back into the tank and out of the filter and engine.

thumb_oilfilter3.jpgthumb_oilfilter4.jpg

Another change was the addition of a “one way check valveâ€. This feature is for those oil tanks that are mounted too high above the recommended oil tank location. It keeps oil from draining out of the tank back down into the engine.

thumb_oilfilter5.jpg

The next change is a new bypass pressure spring. The old filter used a piece of spring steel. This new oil filter has a smooth round edge spring so it doesn’t have any sharp edges to wear through the filter housing. The old bypass pressure was 1.1 bar or 16 psi. This new filter is 1.2 bar or 18 psi. This will stop some filters from opening for a second or two at start up. The old oil filter could be pre-filled with oil which made it easy, but with this filter you can’t pre-fill with oil and you must turn the prop to put oil into the filter before your first start after an oil change.

thumb_oilfilter6.jpg

thumb_oilfilter7.jpg

So you see Rotax has made some fairly big changes to the inside of the oil filter to better help its users deal with their different engine applications. I have attached several pictures so you may see what is actually on the inside. I swore I wouldn’t cut open a perfectly good filter and wait for a used one, but curiosity got the better of me. For the photography critics out there, no I didn’t quit my day job.

I hope this helps you to understand the new Rotax oil filter.

Related Videos are: Oil Filter Installation, Oil Change Procedure, Oil Level Check

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This can be a dynamic topic, but there are certainly some markers to look for in finding yourself a good mechanic that you can really trust to keep you in the air, safe and happy. You probably already have a mechanic, but the important thing is in recognizing if he has more than just the basic skills, but that certain something that gives you the confidence to trust life and limb to him. Let’s examine what the traits are that define “a good mechanic†and steps you can take to find one.

Let’s talk about looking for a good mechanic first. As in any profession, you’ll find varied degrees of competency. Just as in choosing a surgeon, you’ll want to avoid marginal competency and shoot for the elite, or as close to it as possible. Here are a few questions in the determination if whether a prospective mechanic is right for you.

(In the interest of simplification and unencumbered continuity of thought, we will use the pronoun “he†as being asexual.)

  1. Does he come recommended by other aircraft owners?
  2. Do you hear from others that he does a satisfactory job?
  3. Does he have experience in your type aircraft and is he qualified to work on your Rotax engine with the proper iRMT ratings?
  4. Do you hear the prospects name brought up favorably in conversations?
  5. When you talk to the prospect, is he friendly, helpful and patient before the subject of fees is discussed?
  6. Ask the prospect if he has the service bulletins (SB’s) and all the manuals for your engine and fuselage on site?
  7. Is your prospect familiar with the tips, tricks and technical procedures for your Rotax Engine as shown on the Rotax Owner Videos.
  8. How many aircraft like yours has he worked on or inspected?
  9. Does he keep you abreast of issues he found and answer your questions knowledgably?
  10. What’s his philosophy regarding regular and preventive maintenance?
  11. Is he a self absorbed mechanic, or open-minded to your ideas, suggestions, concerns and will he research problems including Rotax Owner videos and forum?
  12. Does he use an inspection check list, discrepancy list and do accurate, detailed logbook label entries? (Possibly ask to see a couple of his labels and check lists)
  13. Does he document well? It’s for your benefit as well as his legal protection.
  14. Does he give you copies of the maintenance check list, or other documents for your personal file? This should be an absolute in case you need it for the FAA, insurance and the re-sale of your plane. You’re paying for the work, get it the way you want it not him.
  15. Does he seem to have the proper tools and education for your particular plane?
  16. Last, but not least and this item is not a real marker of the mechanic’s professionalism, but should be kept in the back of your mind. What is the charge? If the price sounds too good to be true then there may be a reason for it and you might get exactly what you paid for. Caveat emptor. Now I know this is not necessarily always true that’s why this is last consideration while looking for a mechanic that you have compatibility with and do the job that you expect and deserve.
  17. Ask the prospect if he has access to the Service Bulletins

Your life might be in the hands of the mechanic. Strive for one who displays all or most of the attributes shown above.

The mechanic’s motto should be: If there is a problem with your aircraft, major or minor, I’m going to find it. Your safety is priority one.

Due to a plane’s wear and tear, loosening of attachment items or just sitting for extended periods things change and it’s your mechanics job to find these. He needs to be a skilled hunter of problems and an organized repairman for these items.

You’re probably already use or have used, a mechanic. Use these questions, and your own, to determine if he is right for you. If there are some areas about which you wish your mechanic would do better then sit down with him and explain your issues and concerns. You’re the boss. The right mechanic needs to live up to your expectations.

Life is full of choices. We chose doctors, lawyers expecting them to be honest; to work in our best interests; to be receptive to our needs. You fully expect understanding and consideration of your input. Chose your mechanic in the same way.

This was a long story and maybe I should have started it “Once upon a timeâ€, but I hope this helps someone in having a good sound relationship with their mechanic and make their flying safe, reassuring and fun.

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p_newpump.pngRotax has introduced a new fuel pump assembly for the ROTAX 912 series aircraft engines.

This new style pump does not mandate that old style pumps be changed, it is only an up-dated replacement part now available in spare parts and supplied with new engines.

The new fuel pump will be introduced on new engines manufactured from early May onward. Replacement fuel pumps will be available as spare parts with Rotax part numbers as follows:

Fuel pump with barbed hose fittings - Rotax part number 893110

Fuel pump with attached fire-sleeved hoses - Rotax part number 893114

The following will provide more information including photographs, diagrams and special installation considerations.

Details on the new fuel pump assembly can be found in the latest revision of Rotax Service Instruction SI-912-020/914-022 Revision 5. Specific serial numbers of engines which have the new fuel pump already installed during manufacturing can be found in chapter 73-00-00, section 4.1 of the Service Instruction. The Service Instruction document can be downloaded for all 912 series engines by clicking on the link below:

SI-912-020/914-022 Revision 5

Some important considerations for this new style fuel pump assembly:

new_pump1.png

  • When installing the fuel pump, a new isolating flange (gasket) must be used.
    In addition, the new fuel pump requires an o-ring (part # 631870) between the
    fuel pump assembly and the isolating flange (part # 950228)
  • A "drainage line" must be attached to the bottom nipple fitting to accommodate
    potential overflowing fuel / oil in the event of internal pump diaphragm or seal
    failure. This drainage line must be routed to an appropriate area away from hot
    engine parts etc. It is important that the drainage line be routed to a ram air and
    vacuum free zone, it must NOT be routed into the slipstream. The drainage line
    must have a continuous slope downward and must be protected from blockage
    (e.g. formation of ice).
  • Maintenance requirements include inspection of the drainage line for damage
    including blockage.
  • The fuel pump cover assembly is held on with 7 screws. This is for assembly
    purposes only during manufacturing, the pump is not rebuild-able nor is it intended
    that it be disassembled for maintenance.

For more information on parts availability, installation or maintenance, please contact your nearest Distributor, Service Center or Repair Center.

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p_flywheel.pngWith the recent release of Mandatory Rotax Service Bulletin SB-912-050 / SB-914-041, you may well ask "Is my engine affected?" and if so, "What do I do about it?".

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Firstly, some background on the reason for this bulletin release.

There was an issue found with incorrect hardness of certain crankshaft protection washers. This washer is found under the bolt and lock-washer holding the flywheel in place on 912 and 914 series engines. In the interest of safety, Rotax requires the replacement of all washers that were in that production batch of washers. This batch of washers was used during production of engines with certain serial number ranges. Older engines and newer engines of a higher serial number range are not affected by this bulletin.

*

"Is my engine affected?"

The Service Bulletin lists specific serial number ranges of engines affected. TWO separate Service Bulletins were released, one for Certified engines, one for Non-certified or UL engines. The serial number ranges are different for the Certified and the UL engines. The Service Bulletin can be downloaded for either Certified, or UL engines by clicking on the links below:

SB-912-058/914-041 for CERTIFIED engines

SB-912-058/914-041-UL for UL or NON-CERTIFIED engines

Technicians doing the replacement will want to make sure to refer to the applicable Service Bulletin for the correct serial number ranges.

Older engines which have a serial number below those listed in the bulletin(s), and newer engines with a serial number higher than those listed in the Service Bulletin(s) are NOT affected, and do NOT need the washer replaced.

*

IMPORTANT NOTE:

Many of the affected engines were still in the inventories of Rotax Aircraft Engine Distributors at the time of the Bulletin release and may already have had the Bulletin complied with and the washer replaced. Owners and Technicians should check the engine log book to verify if the engine has already met compliance with the Bulletin.

*

"My engine is affected, what do I do now?

If your engine falls within the applicable serial number ranges stated in the Bulletin, the Crankshaft protection washer must be replaced.

It is recommended that this work be performed by a Rotax Service Center, Repair Center or iRMT (independent Rotax Maintenance Technician). To find service in your area, Click Here.

In order to replace the Crankshaft protection washer, the flywheel bolt must be removed. Before removing the flywheel bolt, the crankshaft must be locked in place.

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p_lock.png Rotax-Owner.com has released a short video describing

the process of crankshaft locking.

This video can be viewed by Clicking Here.

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*

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The procedures for replacement of the crankshaft protection washer, and torque values for the flywheel bolt can be found within the Service Bulletin.

Upon completion of the crankshaft washer replacement, the engine log book must have an entry to indicate that the bulletin has been complied with.

*

The Rotax network of Distributors, Service Centers and Repair Centers will have details of any Warranty coverage for the replacement of the washer. Please contact your service provider for details or questions about this bulletin.

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p-tips.jpgThere are several factors that can cause or influence engine roughness, especially at lower RPM's.

A rough running engine can sometimes be a combination of several contributing factors.

One cause of Low RPM roughness can be carburetion.

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Issues such as non-synchronized (unbalanced) carburetors or incorrect fuel mixture settings (too "rich" or too "lean) can cause engine roughness at low to mid RPM ranges. Prolonged engine roughness can cause accelerated wear in engine and airframe components. Components such as gearbox (see our previous Blog on engine roughness) that have been worn by rough running due to carburetion issues can cause additional engine roughness and vibration, which can cause carburetor wear etc. If not addressed, these issues can become a wicked cycle. Regular inspection and maintenance of the carburetors is important.

*

Carburetion issues often show up as high, or rough Mag Drops.

Even though initially one might think of a mag drop issue to be related to an ignition issue, this is often not the case. Unless there is a marked difference in RPM drop between the two mag checks, a high mag drop, or a noticeable roughness when running on one mag or another is often caused by carburetion issues.

*

Improper Fuel / Air ratio.

The Fuel / Air mixture in the mid range is adjustable by moving the jet needle up or down, allowing more or less fuel into the carburetor.

Carburetors that are set too "rich" or too "lean" can cause your engine to run rough, especially in low to mid RPM range. Most commonly carburetion mixture problems show up when the carburetors have been removed and dis-assembled for inspection or routine maintenance, or when mixture is intentionally altered for environmental changes such as a change from winter to summer operation. When dis-assembling the carburetors for cleaning or maintenance, It is important to ensure this jet needle position is noted and returned to its original location upon re-assembly. The position of the jet needle can be changed to accommodate environmental changes from summer to winter, or a significant change in altitude. For more information on changing jet needle position, CLICK HERE to watch the Rotax-Owner.com VIDEO covering this operation, or look in the Rotax Heavy Maintenance Manual, Chapter 73-00-00, Page 12, Section 2.8.

*

Non-synchronized Carburetors:

A Rotax 912 / 914 series Aircraft Engine has two carburetors, each carburetor supplies fuel / air mixture to two cylinders. If these two carburetors are not delivering the same fuel / air mixture to all cylinders, engine roughness can occur. This roughness will be more pronounced at low to mid RPM range. Pneumatically balancing (synchronizing) the carburetors can significantly reduce engine roughness at low RPM. Balancing should be done at engine installation, when carburetors or throttle cables have been removed for maintenance, and at every 100Hr inspection interval. For more information on Carburetor Balancing, CLICK HERE to watch the Rotax-Owner.com VIDEO covering this operation, or look in the Rotax Line Maintenance Manual, Chapter 12-00-00, Page 31, Section 10.

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p-tips.jpgThere are several factors that can cause or influence engine roughness, especially at lower RPM's.

A rough running engine can sometimes be a combination of several contributing factors.

One cause of Low RPM roughness can be a gearbox with low spring pack tension (or a "loose" gearbox).

*

Keep in mind that even though the Rotax Operator's Manual for the 912 and 914 series does allow for a minimum idle of 1400RPM, it is recommended to keep the RPM a little higher to reduce roughness and engine wear. 1800 - 2000 RPM is a good place to set your idle. Prolonged idling at low RPM's can cause accelerated wear in gearbox components, which can cause increased engine roughness. Low idling and rough running can also cause wear in other components such as carburetors. Worn carburetors can cause engine roughness - it can become a wicked cycle. Therefore, proper maintenance of the gearbox is important.

*

The Rotax 912 / 914 series gearbox serves two main purposes:

*

1) To reduce the crankshaft RPM to a slower RPM for the propeller.

2) To act as a tortional dampening system to absorb the piston pulses of the engine which fight against the flywheel effect of the propeller.The tortional dampening system consists of a pair of metal "dogs" which ramp against each other. When a piston pulse is transferred through the gearbox, these dogs ramp against each other and the force is absorbed by a set of disk springs (spring pack) holding these dogs against each other. These metal dogs and disk springs do wear over time and will loosen the spring pack tension within the gearbox. When the gearbox spring tension loosens, the tortional dampening system is less able to absorb the piston pulses. This will result in more vibration and a rougher running engine at low RPM's. Over time, a "loose" gearbox will cause excessive wear to gearbox components as well as transferring unwanted vibration to other engine and airframe components. A "loose" gearbox can also cause hard starting issues. Engine roughness or vibration caused by low gearbox spring pack tension can slowly increase over time, as the gearbox wear increases and the spring tension decreases.

*

Fortunately, if your engine is equipped with an overload clutch for propstrike protection (often referred to as a "slipper clutch"), there is a simple way to determine if the disk spring tension within your gearbox is within acceptable limits. This is called checking the "Friction Torque" of your gearbox. You may hear this procedure being refereed to "checking the spring tension" or "checking the shimming" of your gearbox. Rotax Owner has produced a VIDEO covering the procedure for checking Friction Torque and can be viewed by CLICKING HERE. Within this video are steps to determine whether your gearbox is equipped with an overload (slipper) clutch or not, as well as the steps to check the friction torque on an engine equipped with an overload (slipper) clutch.

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If your engine is not equipped with an overload (slipper) clutch, the disk spring tension within the gearbox is just as critical, however there is no means of checking the spring tension other than removing the gearbox and physically checking this on the bench.

*

"Friction Torque" checking of your gearbox is an important part of your scheduled 100 hr interval inspection. Keeping the friction torque of your gearbox within limits will help ensure a smooth running and smooth idling engine, reducing wear and prolonging the life of all engine and airframe components.

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Gentleman can anyone advice the proper sparkplug gap for a 618? I start to have about 300 degrees diference between the EGT readings and I want to start trouble shooting from the plugs, ANy other advice will be apreciated.

Regards to all

Yanis

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Is it possible to flood the engine when applying the choke and the fuel pump ON simultaneously?

If yes what is the remedy?

It started without problems the day before but today I could not start the Rotax912 UL and waited a while but it would not start.

Try again tomorrow.

Best regards Jan

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Ok I guess I'll be the first to ask. Does anyone know or have a good guess at what the March 8th Evolution is going to be? I have heard on a different forum that there could be an April announcement about 912 fuel injection. What do you think?

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Hi All

I have a 912s and one of my carbs is overflowing I stripped and cleaned the carb and replaced the check valve all seemed fine for a while but it's overflowing again Any ideas?

Regards

Finbarr Lynch

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I need to replace an old automotive radiator in an open air pusher configuration with a 912S engine. The easiest way would be to install a Rotax #995699 radiator. This radiator is designed for the two cycle engines and it's cooling area is 20% larger than the 912 radiator. It also requires no header tank. The only drawback I can see is that the inlet and outlet sizes on this radiator are 19mm. rather than the 25mm. outlets on the 912 radiator. Will this restriction be a problem?

Bill.

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I religiously turn prop to get all oil burped up into oil tank before startup,

but admit I don't fully understand why.

I get that if I don't do that the some oil will be pooled down where it shouldn't be,

but don't really understand where or how it being there could do damage on startup.

(After all, whereever that extra cupfull of oil is sitting would _seem_ to have to be part of the normal oil circulation path.)

Anyone willing to educate me, or point me to an article that would directly address my question without taking a 3 week factory maintainance course? dizzy.png

Al

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