That rubber coupler saved the engine. Hopefully that gearbox case is not worn or ovaled out with that bearing failure. Would be a good time for an engine/gearbox overhaul weather you need it or not. Glad to hear the news, keep us posted.
Terry, I don't do farce book so I won't see the pictures you mentioned. IF you're getting "irregular throttle response in the midrange", I would carefully check the engine for signs of either detonation or seizing. If a two stroke partially seizes it can still restart and later give a full on seizure.
Hi Terry. I would say is that your engine is fine. A twostroke lives and dies on its crankcase seals and it's exhaust. If a seal is leaking it causes the engine "wisker" the spark pluges and stall. If the exhaust carbones up you will loose almose all the power and eventually the engine won't run at all. It is of the utmost importance that the crankcase is sealed. Not even a pin prick of a leak, and the exhaust is kept free of carbon. Even if the exhaust falls off the power loss would be insignificant. Only if you were to have fitted an expansion box tuned exhaust system would the power loss be noticeable. Bad sealling of the crankcase would cause a very unreliable engine. The rubber connection in the gearbox is where your trouble lies. Haveing owned an Alfa Romeo in the past I see a weakness in design of the shock absorbsion system. There is no pilot bearing in the input shaft or a pilot shaft on the output shaft. This arrangement is there to hold the rubber connector centred like a clutch plate on a car. What I think happened in your case was the bearing failed causing the input shaft and the doenut to drop out of centre. Then the bearing locked up causing eccessive strain on the dienut. These two conditions caused the doenut to break up into pieces. Did you expierence excessive vibrations just before failure? If so I would leave the engine alone and concentrate on the prop reduction unit. 96 P.S.I is very close to 100 P.S.I. and twostroke engines are a very low compression engines anyway. Just keep a close check on the spark plus. If you see any signes of fouling then check the crankcase seals and gaskits. The crankcase seals are the major cause of a twostroke engine been unreliable. Even a blowen head gaskit doesn't mess up the reliability too much just cause a loss of power. I've had motor bikes where the head gaskit has blown and the only thing noticeable was the flame that appeared out of the top end, but a blocked exhaust or a leak in the crankcase was a totally different matter.
Hi again Terry. You pointed out another problem with the exhaust system. First off I want to say that I'm not a lover of siamese exhaust systems on twostrokes. I feel you will have better performance if you had seperate stacks for each cylender. Siamese systems tend to blow crankcase seals when they block up. This was told to me when I had a Suzuki 750 GT. There was a 3 into 1 system available for these engines. I was told they were engine destroyers and that I would be wise to fit the standard 3 into 4 system. When you did the compression test did you remove both plugs and set the throtle to fully open, and was the engine at operating temperature. If you omitted to do any of the conditions mentioned it will give you a low reading. I suggest that you run the engine while you have the reduction drive off and re do the compression test with a hot engine and the spark plugs removed. Just remember to open the throttle. I think you will be in for a pleasent supprise. Your comptession should go up to about 120 PSI or there abouts. Compression tests always are done at full throttle and a warm engine. Just remember all the spark plugs must be removed or at least disconneted. The test is done at cracking speed anyway. Best of luck with the repair. I hope the bust up didn't do too much damage to the reduction drive.
Can you drill and tap the gearcase and install a chip plug? I am a career helicopter pilot and chip lights aren’t uncommon at all, would warn you of an impending failure in the reduction box well before you have problems.
the bearing spun in the case, the case got hot, the heat transferred to the donut, it decompiled, the rubber donut parts (probably was only one large piece at first) acted like a brake between the crank and the housing and just stopped the crank (you can see it in your flight video). The case cooled as you descended, the rubbed dislocated and freed the prop, you can see that as well in the flight video, then you restarted it. The case may or may not be damaged from the spinning bearing outer race where that bearing slides into the case for the gear drive..
Glad you found the problem. It was also good that you didn't try to fly it home from the other airport. I'm not sure you will be able to use the old redrive case. It looked like the outer bearing race was rotating. If the outer race of the bearing can rotate in it that's not good, that's supposed to be a press fit. Can't wait to see you back in the air again. Good luck.
Hey Steve, could it have been a damaged or faulty case that somehow allowed the bearing to loosen, and caused the leak, or do you think a seal or gasket failed, causing the leak, and the bearing to fail?
@@kirbylee57 I can't tell where the oil leaked. I didn't see any evidence of a leak on the front of the plane, like where the engine mounts. I don't know if Terry did any cleaning of the parts, they all look like he has. It's hard for that much oil to get out of that case and not make a big mess somewhere on the engine. I don't think the case caused the bearing to loosen. I think the bearing seized, due to no lubrication and caused the outer bearing ring to spin which caused the case to be damaged. What caused the oil to be gone is a mystery. The seal at the prop shaft, or engine shaft, usually wears over time and a leak there would be evident by oil being on the prop, or the engine. A gasket failure is rare since there is no pressure to cause one to blow. It would also cause oil to be visible somewhere on the engine since it would be blown around by the wind and prop blast. Worst case would be that the oil was drained and none put back in.
ThesevRotac engines and gear boxs are not reliable after 300 hours which is the TBO and need to pull apart and change bbearing every 300bhours andba completebover haul and maybe every 5byeats which ever come first . I know a few guys hate these rotax engines
That rubber coupler saved the engine. Hopefully that gearbox case is not worn or ovaled out with that bearing failure. Would be a good time for an engine/gearbox overhaul weather you need it or not. Glad to hear the news, keep us posted.
Terry, I don't do farce book so I won't see the pictures you mentioned. IF you're getting "irregular throttle response in the midrange", I would carefully check the engine for signs of either detonation or seizing. If a two stroke partially seizes it can still restart and later give a full on seizure.
Hi Terry. I would say is that your engine is fine.
A twostroke lives and dies on its crankcase seals and it's exhaust. If a seal is leaking it causes the engine "wisker" the spark pluges and stall. If the exhaust carbones up you will loose almose all the power and eventually the engine won't run at all. It is of the utmost importance that the crankcase is sealed. Not even a pin prick of a leak, and the exhaust is kept free of carbon. Even if the exhaust falls off the power loss would be insignificant. Only if you were to have fitted an expansion box tuned exhaust system would the power loss be noticeable. Bad sealling of the crankcase would cause a very unreliable engine.
The rubber connection in the gearbox is where your trouble lies.
Haveing owned an Alfa Romeo in the past I see a weakness in design of the shock absorbsion system. There is no pilot bearing in the input shaft or a pilot shaft on the output shaft.
This arrangement is there to hold the rubber connector centred like a clutch plate on a car.
What I think happened in your case was the bearing failed causing the input shaft and the doenut to drop out of centre. Then the bearing locked up causing eccessive strain on the dienut. These two conditions caused the doenut to break up into pieces.
Did you expierence excessive vibrations just before failure? If so I would leave the engine alone and concentrate on the prop reduction unit.
96 P.S.I is very close to 100 P.S.I. and twostroke engines are a very low compression engines anyway. Just keep a close check on the spark plus. If you see any signes of fouling then check the crankcase seals and gaskits.
The crankcase seals are the major cause of a twostroke engine been unreliable. Even a blowen head gaskit doesn't mess up the reliability too much just cause a loss of power. I've had motor bikes where the head gaskit has blown and the only thing noticeable was the flame that appeared out of the top end, but a blocked exhaust or a leak in the crankcase was a totally different matter.
Hi again Terry. You pointed out another problem with the exhaust system.
First off I want to say that I'm not a lover of siamese exhaust systems on twostrokes. I feel you will have better performance if you had seperate stacks for each cylender. Siamese systems tend to blow crankcase seals when they block up. This was told to me when I had a Suzuki 750 GT. There was a 3 into 1 system available for these engines. I was told they were engine destroyers and that I would be wise to fit the standard 3 into 4 system.
When you did the compression test did you remove both plugs and set the throtle to fully open, and was the engine at operating temperature. If you omitted to do any of the conditions mentioned it will give you a low reading.
I suggest that you run the engine while you have the reduction drive off and re do the compression test with a hot engine and the spark plugs removed. Just remember to open the throttle.
I think you will be in for a pleasent supprise. Your comptession should go up to about 120 PSI or there abouts.
Compression tests always are done at full throttle and a warm engine. Just remember all the spark plugs must be removed or at least disconneted. The test is done at cracking speed anyway.
Best of luck with the repair. I hope the bust up didn't do too much damage to the reduction drive.
Good luck on the repair Terry
Glad you and the plane are all right,
Oh wow Terry it looks like you found the problem I am glad it was not the engine itself 👍😁
Nice one, Terry. Hope you get airborne again soon. All the best.
Can you drill and tap the gearcase and install a chip plug? I am a career helicopter pilot and chip lights aren’t uncommon at all, would warn you of an impending failure in the reduction box well before you have problems.
the bearing spun in the case, the case got hot, the heat transferred to the donut, it decompiled, the rubber donut parts (probably was only one large piece at first) acted like a brake between the crank and the housing and just stopped the crank (you can see it in your flight video). The case cooled as you descended, the rubbed dislocated and freed the prop, you can see that as well in the flight video, then you restarted it. The case may or may not be damaged from the spinning bearing outer race where that bearing slides into the case for the gear drive..
Glad you found the problem. It was also good that you didn't try to fly it home from the other airport.
I'm not sure you will be able to use the old redrive case. It looked like the outer bearing race was rotating. If the outer race of the bearing can rotate in it that's not good, that's supposed to be a press fit.
Can't wait to see you back in the air again. Good luck.
Hey Steve, could it have been a damaged or faulty case that somehow allowed the bearing to loosen, and caused the leak, or do you think a seal or gasket failed, causing the leak, and the bearing to fail?
@@kirbylee57 I can't tell where the oil leaked. I didn't see any evidence of a leak on the front of the plane, like where the engine mounts. I don't know if Terry did any cleaning of the parts, they all look like he has. It's hard for that much oil to get out of that case and not make a big mess somewhere on the engine.
I don't think the case caused the bearing to loosen. I think the bearing seized, due to no lubrication and caused the outer bearing ring to spin which caused the case to be damaged.
What caused the oil to be gone is a mystery. The seal at the prop shaft, or engine shaft, usually wears over time and a leak there would be evident by oil being on the prop, or the engine. A gasket failure is rare since there is no pressure to cause one to blow. It would also cause oil to be visible somewhere on the engine since it would be blown around by the wind and prop blast. Worst case would be that the oil was drained and none put back in.
glad you found it terry. good luck
nice to see the engine didn't burn up!
Good information. Thanks Terry.
Looks like your motor is fine. I would suggest replacing all the bearings on the redrive
Thats why I prefer a Belt Drive..
what is the total weight on your engine setup? thanks
Did you see exactly where the fluid leaked from? Was it from a gasket or seal that simply failed, or did it leak around the bearing area?
The housing where that bearing spun IS DAMAGED. I think you will need a new one.
how do you know that?
@@kirbylee57 Because the bearing race spins, it should be press fit, means held tight by the casing for the bearing to do it's job.
It could be glued in but is not a good repair specially in an airplane.
A good machinist could put an steel insert but i don't know if there is room for it.
Thanks for sharing, how many hours total are logged on your engine?
that donut looks like the guibo out of a bmw e30 or merkur xr4ti
T bird flights
ThesevRotac engines and gear boxs are not reliable after 300 hours which is the TBO and need to pull apart and change bbearing every 300bhours andba completebover haul and maybe every 5byeats which ever come first . I know a few guys hate these rotax engines