Ever since I started flying I've been having problems with this engine. On my first flight I lost the back half of my muffler, but that was only a sign of things to come. Everytime I started flying, the engine would come to life, have full power, and it would fly great. After about 5 minutes, the engine noticeably starts to lose power, and maybe after 10 minutes I have to bring it down before the engine dies (which has happened a few times) Everyone at the field would just tell me it's because it's a new engine, but after going through more than 10 tanks, and not noticing any improvment from the first flight, I'm starting to doubt that claim. It finally caused me to crash last Thursday by dieing right after taking off on a second flight when it was still hot from the first.

After I fixed the plane back up, I've had nothing but trouble with the engine. When giving it full throttle from idle, it will get a lot of power, then slow down, then speed up a little more than it slowed down, it does this several times gradually moving up to "full" power. I say "full", because at full power it only gets enough power to actually drive around on the grass field. It doesn't have a chance to get off the ground. Even if it did, I would probably still have the problems with it losing power after a few minutes and having to bring it back down.

I noticed that a large pool of fuel is building up on the bottom of the muffer. I'm kind of figuring that it's fuel from the exhause coming around but it seems kind of excessive and didn't exist pre-crash. I'm kind of thinking there is damage and it's leaking somehow, but then again, it could be nothing. Could someone explain what might be the cause of this?

The engine I have is a .46 Magnum GPA (I dont even think they make this anymore. I got it 4 years ago but only started using it a few weeks ago). I'm using 15% nitro, synthetic/castor 80/20 wildcat fuel.

I really can't tell a change in performance from making it half a turn richer or leaner. I don't really want to move it a lot from the place where the people who know what they're doing set it. I don't know what the engine manufacturer recommends; god only knows where the manual is.

Does anyone have any clue what could be wrong with my engine? I'm about to go buy a new one tomorrow, but I don't want to blow a lot of money away because of my incompetence.