I have an Evolution 61 on my 4-Star and has been running great for the past 3 years with no problems. This past weekend after flying, I saw black all over my plane from the exhaust. Normally your plane gets all oily from glow fuel, but this was black ! It took a lot of windex and alot of wiping to get it all off. Any ideas ?

That's usually your engine puking itself out. Aluminum from the piston, most likely.

Or a loose muffler.

If the engine seems to still run fine, then MinnFlyer has the answer.

Bruce

The best thing to do right now is spend a couple of dollars and buy a threaded 4-40 rod. Cut this the length you need to run from the front of the muffler to the rear end. Just use this with nuts on the front and rear to hold the muffler halves together. This is an improvement anyway. While your muffler is apart you can take out the baffle if noise isn't an issue in order to game a bit more power. Look over the mating surfaces of the muffler before reassembling.

If this isn't your problem, come back here to find out what you need to do next.

I have the .36 and it did the same thing. There is a small silicone gastket between the two parts of the muffler and this wears out with time. As the exhuast builds up heat when the engine runs, the bolt in the exhaust grows a bit and the back end of the muffler rotates as a result of the natural vibration of the engine. All I did was to put some teflon plumbers tape around the flange of the muffler to create a new seal. Also, run the engine up to operating temperature and then tighten the bolt.This will stop the back-end of the exhuast from turning.

Hope this is helpfull.
Good luck

OK thanks for all the replies. Now I have an idea of what to do.