Sounds interesting. How do you raise compression and advance the timing on a Honda GXH or Huangsheng copy? Are there drawbacks?Most small utility engines are designed to tolerate crappy fuel. They have (relatively) low compression and tame ignition timing. This allows them to run properly on fuel that has degraded quite a bit from storage.
This also allows quite a bit of performance gain if you raise compression ratios and advance the ignition timing. (Briggs, Tecumseh and Honda kart engines are a good example)