I had a perfectly good running cb125s which I decided should have a 145cc cylinder and piston on it because at the time I was bored and needed something to do. Got the engine back together and back in the bike and for the life of me I cannot get it to run right. Starts and idles perfectly and has great power until exactly half throttle when it starts to run like it is hitting a rev limiter. Absolutely no power, missing, but no smoke or anything. Does it in neutral and under power. Carb is clean as a whistle, originally had a 95 main jet in there but have tried everything from it to a 125 with no change. Valve clearances are dead on, points are set, I believe the timing is right. No airleaks on the carb or anything. Ignition advance is working. Can anyone help? Its driving me nuts :/