have recently bought a KTM 125 motocross bike. I got this bike cheap as it starts and runs but will not rev to its full potential. I havefitted a new plug, stripped and cleaned the carb, decoked the exhaust but to no avail. The bike starts first time without any trouble and will rev up to about 1/4 throttle but any more and the whole engine bogs down and will not rev any higher. By holding the throttle wide open it puffs and splutters and tries to blow the exhaust off, I believe this to be a backfire? does anyone have any ideas of where I should be looking to solve this problem. many thanks. nigel.