Rotax 912 ULS - Fretted CrankCase

Re: Rotax 912 ULS - Fretted CrankCase

by Roger Sheridan » 11 years ago

Roger Sheridan

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Hi Everyone & thank you for the informative thread.

I have recently bought a 200hr 912ULS which is being rebuilt by an experienced 912 engineer.
Unfortunately the s/n is 5645371 so I am anxious about the fretting issue.

I have read that the specified flange sealant was changed from red loctite 515 to black loctite 5910 which may make a difference.

Did you find evidence of any assembly problem on your engine Jonathan?, was there sufficient sealant on the flange?, which product did you use?

Since my cases are undamaged it would seem unnecessary to replace them but I would be very grateful for any ideas to stop the problem arising later on.

Best regards,

Roger (UK)

Re: Rotax 912 ULS - Fretted CrankCase

by Przemysław Wiśniewski » 11 years ago

Przemysław Wiśniewski

65 247 3

Hi. I have a question, if you had any metal contamination in oil filter and/or magnetic plug?

Re: Rotax 912 ULS - Fretted CrankCase

by barry Norman » 11 years ago

barry Norman

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I finally got my crankcase split today and confirmed it was crankcase fretting. It looks just like Jonathan's pictures. The bearings show wear but no brass is exposed. The crank measures 1.7495 inches on all three journals. The journals appear to be in good shape but could stand to me polished a little. Everything else looks good. There's a little metal the the piston shirts on number one piston and some very light corresponding scratches in the number one jug. Nothing to really worry about.

Jonathan, which bearings did you order for yours? There are two different ones listed.

Re: Rotax 912 ULS - Fretted CrankCase

by Jonathan Elliott » 11 years ago

Jonathan Elliott

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Hi Roger

Sorry to hear you are potentially in the effect S/N range too, you have quite a low hour motor by the looks of things although hours don't seem to make much difference as there have been some large variations in the number of hours reported upon failure.

From memory our faulty crankcase had the red Loctite in it. There were no apparent assembly issues with the engine. Its hard to say if there was sufficient sealant on flanges. During assembly of our new crankcase we installed the black 5910 Loctite. I should mention that in the southern hemisphere (well certainly in New Zealand) that Loctite is actually marketed under a different product number. If anyone is interested in what that is I can check and let you know.

I would not worry about the problem until you get some indication of tightness when turning the engine over ... hopefully it will never happen. To be honest I have no idea about stopping the issue from happening.

Regards,
Jonathan

Re: Rotax 912 ULS - Fretted CrankCase

by Jonathan Elliott » 11 years ago

Jonathan Elliott

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Hello

No the engine showed no signs of making metal prior to the failure. Even once the crankcase had failed there was very minimal fragments in the filter and plug.

Regards,
Jonathan

Hi. I have a question, if you had any metal contamination in oil filter and/or magnetic plug?