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Conrod Bearing Tester.


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A local pilot has had an engine failure with his Rotax 582 grey head because of a crankshaft bearing failure and I`d like to allert everyone using a " Conrod Bearing Tester",(the type that pressurises the crankcase) to be aware,this pilot owns his own test unit and has been testing the engine regularly at 10 hourhly intervals.


The engine had done 375 HRS and had been tested 5 HRS before the failure and the test showed no indication that the bearings were suspect.


Fortunately, a safe landing was carried out onto my strip and no damage was done to pilot or aircraft.


There is more than one reason for bearings to fail and it is difficult to know exactly why, however, be aware that this type of test can cause a false sense of security.





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Bearing tester.


I have doubted the efficacy of this method of testing bearings all along. As you say it can give a false sense of security. You can usually count on 400 hours. The reason that clearance is not an indication is the nature of a roller and a ball bearing.. They do not develop "play" in the normal sense but fail due to fatigue of the surfaces resulting in "flaking" of the surfaces. At this point the bearing is well and truly failed even though there may be little play. The bits of hard metal are wrecking tha cages of the bearings and being released into the rest of the motor, scratching and scoring everything. Sometimes the big end will just get very hot and seize partially or completely, and the rod comes out the side. Nev.



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Guest Maj Millard

Castrol TC-W3 is an outboard oil for boats....Wrong !!


I personally only ever used Castrol Active 2T (red) for years in my 582, and never had any problems. You don't need the TTS which is full synthetic. I'd say the oil is his problem.


Refer to Rotax Service Instruction SI-2ST-008 Dated April 14.09


Selection of suitable operating fluids for Rotax 2-stroke UL engines.


I quote : "Oils that are intended for marine(watercooled) 2 stroke engines are not suitable for use in UL engines, due to their low operating temps.


Oils formulated for air cooled engines are recommended, due to their high temp properties"...... end quote.


There are only nine oils listed on their recommended oils list, none are Valvolene, and top of the list is Castrol Active 2T..............................


Frank, you can view or download the Service instruction from the RAAus site.....Maj



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When manufacturers bench test new engines, sometimes an issue or two comes up where it's too late or impracticable to redesign the engine.


e.g. oil galleries are too small.


Alternatively, they may find that temperatures in parts of the engine are not what they expected.


In many cases they can solve the problem and get life cycle durability by using specific lubrication properties relating to viscosity, temperature, pressure etc.


This seems to be happening more and more.


Personally I think it's a cop out, and the engine should be redesigned or at least get a break point update, but realistically with some modifications requiring thousands of engineering hours and perhaps millions of dollars in tooling this is unlikely to happen.


As a result, it is no longer safe to just pick a popular oil and use it in all your engines.


If a manufacturer specifies a list of recommended oils, I would strongly recommend adhering to it because there's probably a good reason.


Failure, binding, seizing etc. can come very quickly.


I've got a 4WD where the galleries were made too small, and I'm committed to buying oil in 20 litre drums at about $15/litre, but the alternative is a several thousand dollar engine rebuild well before time.


Having said all this I am not implying that these are the reasons for the Rotax list, or that Rotax have any issues at all - the problem may have been caused by something completely different, I'm suggesting that with any product where a loist of lubricants is provided for various components, it's important to adhere to that list.



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Guest Maj Millard

No problems Frank, unfortunatly he's probabily got a bit of work to do now, but get him on Castrol Active 2T when it's all back together. As far as the crank-play tester goes, Peter Goften would check mine every now and then (he's got the tester), and mine had normal wear all through it's life, and was still well in limits last check, which was around 550 hrs. Cheers Ross.......................................024_cool.gif.7a88a3168ebd868f5549631161e2b369.gif



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I'm suggesting that with any product where a loist of lubricants is provided for various components, it's important to adhere to that list.

Absolutely Correct.


part of the problem is that it`s difficult to determine exactly why bearings fail but if we use the recomended oils,we`re stacking yet another thing in our favour.





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