Ok, here are the engine settings when I last had it running:

- I removed the head and measured the position of the contra-piston. I calculated the compression to be 1:20,44 (assuming that compression is calculated from the point where the exhaust/intake ports are just closed)
- Both the full-throttle and the idle needle were opened about 2.5 turns.
- The carb is a 10mm OPS slider, which opens fully at full throttle.

Assuming I calculated the compression correctly, I don't think this is the problem. Maybe I should try leaning it out more?

Remember, I'm not looking for fuel-efficiency, but for maximum horsepower, as this engine is being used in radio-controlled tractor pulling.