i own a `94 boyou 220 and my problem is when i ride it full throttle for more than 2 minutes it will start to sputter out and then i have to pump the throttle for it to keep going i put a new timing chain in and it is timed perfectly please help..

 

Check for obstruction in fuel tank petcock, fuel lines, carburetor (clean, if necessary); check float valve height and adjust as necessary. Fuel starvation of some kind appears a possibility. Good luck!

Tree Farmer