Im waiting for a flywheel puller from Velocruz. When I get it I will experiment with timing. I have 4 flywheels to mess around with. As far as drilling your jet to a larger size be careful, I had the original Solex carb on my hybrid engine, and it had to run with the enricher nearly full on. I measured the jet @.020, my next drill bit was .024. Close enough I figured, was so rich it wouldnt even run. Went back to the original jet in the HD carb and all was well. I believe the original carb leaks air at the base. The manifold fits it loosley. The original parts have really powered up my engine, what you hve done with the head is Im sure is what has worked on mine also as the Solex head is higher compression than the HD. They must have detuned the HD for poor fuel, which I have heard is common in China.