Hi When my bike is cold it sputters and after 30 seconds of riding gives full power. After I ride for 10 minutes or so, It at times has no power starting off from a standstill. This is worse under more of a load such as starting off to go up a hill. This problem is intermitant and has gotten worse over the last 2 months. Any ideas? I have cleaned the airfilter and changed the plug a couple of times. The clutch is not slipping. It seems to be a carburator problem. The air cleaner is contacted properly to the carburator. At high speed it seems to go good. I can do up to 80 km on a hill.