I have a .60 size p-51 mustang with an evo 60 mounted inverted on it. When i start the motor it will die off after about 45 seconds, and i cant get to idle down to a reasonable rpm. When i give it full throttle, it reaches max rpms then loses some rpms and eventually dies off.

I think it is too lean, but i richen it a lot and it still doesnt help. The fuel tank is located almost in line with the carb, maybe just 1/16th of an inch below. It is using a os 8 plug with omega 10% fuel and an apc 13 x 6 propeller. I think it is a muffler problem. It is an after market pitts muffler. With this muffler, the motor is much louder than the stock muffler and I think that it is not putting enough pressure back onto the engine. I cant try it with the stock muffler because i bought the motor off ebay and it didnt come with a stock motor, but it MUCH louder than other .60 size motors i have heard. Could it be a muffler problem?

Thanks,
Matt

Make sure the fitting on the muffler isn't stopped up. It does sound like you are lean at top end. You did not say if at idle it is blubbering or smoking quite a bit. I would suspect that the low end (idle) may need to be leaned somewhat.

Turn the plane upside down and start it. Run it up and down and see if it runs differenltly than when started right side up. This may give you some clues. I have a feeling it is loading up while at idle and when started upside down this may not occur.

Jim

Your issues at full throttle sound like overheating symptoms. Check for signs of overheating. Can air freely escape the cowl, aft of the cylinderhead?

Also, start with a 12x6 APC - a 13x6 seems a bit much for that engine.

I checked the muffler fitting and it is not stopped up, also at idle, it seems to be running to lean in that it just dies, it does not produce excess smoke.......but it does transition smoothly, so when i richen it, it idles better, but the transition is awful. I tried an apc 12 x 6 originally and there was almost no difference, I was actually recommended to make the move to a 13 x 6 by the guy at my LHS. It seems like no matter what i do, i am unable to tune the top end, because no matter where i have the high speed needle set, it will always reach max rpms then lose some and eventually die off.


as for cooling, it cant really escape behind the cylinder head, tomorrow i will try it without the cowling just to see what happens, i have never ran it without the cowling, i never thought that might be a problem? will get back to you guys tomorrow afternoon.


Thanks,,
Matt