I am not refering to electronic or mechanical advace, but rather to modify the mounting holes on the magneto into slots so that the timing can be adjusted. I would like to experement with bumping the timing up on my gx31 and compensating with a higher octane gas. I will report my results but I would love to know if anyone else has already tried. The thing that kills me on this engine is it's construction with the head integrated with the cylinder preventing milling down the head to increase compression. That I have the machine skills for, moving the wrist pin upward, stroking the crank etc. I do not.