Stick Jammer

I have an O.S. 46FX in my Somethin' Extra that has about twenty flights on it. The motor runs well but the exhaust oil is quite dark. It's been that way from the very first tank of fuel and it doesn't really matter where the needle valve is set. I've also played around with the idle mixture, no change there either. Any ideas?

GalenB

My Feedback: (18)

What fuel are you using?

GrnBrt

My Feedback: (5)

Check to make sure everything is tight on the motor especially the muffler. If the muffler is even a little loose it will cause this. Galen's right also, what fuel are you using. also when the motor is running at idle put a piece of hard paper in the exhaust for a few seconds and then closely examine it for any metal particles. If you find some then you have an internal problem. My TT .46 PRO did this at first when it was new but it was just the engine seating everything in and was told it would go away and it did, but check anyway.

Stick Jammer

Using Omega 10% I have four other aircraft with O.S. 2-strokes and I burn the same fuel in all of them. That 46 is the only one that has this problem. I removed the muffler to see if there were any signs of metal particles and it didn't appear so, but the exhaust port and that side of the piston are black. Is this thing gonna come apart on me or is it no big deal? I don't have much experience with this sort of situation, I just got started in R/C planes about a year ago. It does seem odd that all my other motors run clear.

GalenB

My Feedback: (18)

A simple remedy/test would be to disassemble the muffler and use a little high temperature RTV from the auto parts store on all of the joints. This will seal them and help prevent the parts from rubbing. As Art has already mentioned -- the most likely cause for the black residue is aluminum dust from the pieces of the muffler rubbing against one another.

If the blackness goes away then you know the problem If it doesn't then it's likely to be more serious and you may want to consider sending the engine in...

Stick Jammer

Thanks for the info guys. I've already sealed everything up with high temp RTV when I had the muffler off but have not run the engine since. I'll let you know when I do and what the out come is.