sounds if though your engine is to rich. Those ofna force 26 motors like to run hot, upwards of 260 degrees. Lean your high speed by 1/2 a turn and go from there. You need to break the motor in, so let it run rich for a couple of tanks before you start to lean it out. Take your time, the key is to make small adjustments on the carb so as to not hurt the motor. If you need more help, post your q's here, of course you probably knew that!