Anyone know any easy an simple performance mods on the huasheng 142. I've bought a 38t sprocket and I'm very pleased to find I can now cruise at 55-60kph or 33-37mph. Which is fine. But my engine won't rev all the way out. It's runs up to about 3500-4000 rpms an just won't pull any harder. I know the redline on these is over 7gs. How do I get more torque out of this little engine ??? Note I've already done the straight pipe an noticed a small amount of hard pull accelerating. But no difference in top end. I am running 7/8-3/4 pipes tho. Should I ditch the 3/4pipe an try going all the way 7/8s...