What nitro % are you using? Ringed engines take longer to fully break in. I have one of these GMS .76 engines and it runs real sweet. I ran about half a gallon of 3% Rossi fuel thru it during break in, then did the adjustments. I would run a couple more tanks thru it at least then try adjusting it again. It took the entire gallon to fully break in. Great engine.
20 years ago