Mine runs like a swiss watch. Two things may be causing this problem:

1. Muffler, you should have a MKII muffler which provides better backpressure to the engine than the original muffler. If your engine was bought new within the last 15 months, you should have the MKII muffler already.

2. Nitro content and plug. Use no more than 5% nitro, use a cheap fox idle bar plug and try again.


Both suggestions are given assuming the rest of your fuel system/setup is properly setup, i.e. fuel tank not too far back, no leaks in fuel lines, tank height is appropriate, the carb o-ring is on the bottom of the carb throat, not seated at the base like 99.9% of engines (check this first, check for pinched o-ring and reseat carb and o-ring but also put a little silicon gel on base of carb as a precaution).

By the way, 300 degrees F temp reading taken at glowplug location is not too hot, You should be at 350 degrees F for best performance but not to exceed 400 degrees F.