Hello guys, The engine turns 8600 on the ground for just a few min. and then it starts acting up, I am using 30% nitro, i have ran the motor without the cowl and it doesn't seem to do it as bad with out the cowl on it but it does sound good on the ground and after a couple minutes in the air it goes sour. This is the SPORT version. The motor has never kicked or backfired. The motor smells really hot when it does running. The fuel system will hold pressure for a long time. The motor Is backed off about 500 RPM from max. So it is running a tad bit on the rich side. ,please let me know. Thank You hw123