I broke in an OS 91 four stroke engine the other day. I couldn't get the muffler to stop leaking. I tried to loosen and re-set the nuts on the stem to engine and muffler. But it kept letting exhaust fluid leak out. I want to try the high temp silicone I bought at the auto parts store. What should I use to get the residue off the threads? I was thinking of using Formula 44. Will that be OK? Or can I just wipe the parts off and apply the silicone?

Thanks for any help.

I use acetone or alcohol to remove any oil residue prior to applying the silicone, most anything that would degrease the threads would probably work.

Acetone works well for me.

I use the regular teflon plumbers tape on the threads into the cyl head.

FBD.

Thanks for the quick responses guys.

Teflon tape? Hmm. I wish I thought of that before I got the silicone. Will it really stand up to that kind of heat? I'm not sure how much heat these engines put out. I do know that the plumbers tape needs to hold up to at least 130 degrees. Sounds interesting.

Yes, teflon will hold up to very high heat. I had problems with the
head-pipes coming loose, and oil making messes on the cylinder heads.

The teflon tape fixed all the problems at the same time. I was afraid the
threads would get beaten out of the head, with the head-pipe getting
loose.

Remember to retighen the nut after each flight (3 or 4 times) until the
threads "bed-in", and it stays tight.

Dave.

Bruno:

The Teflon tape FBD mentioned will stand a lot higher temp than the RTV silicone, evedn the high temp version. Exhaust temp on a four stroke can reach 600F, so select material accordingly.

Bill.

Thanks guys, I really like the tape idea.