Check spark plug for fouling and gap clearance. Check spark plug cap. Check the high tension cable from the spark plug to the coil for damage. Check the clearance between the coil and the magnets with a business card. Check the throttle on the carbie to make sure that the earthing of the coil is not ON - which shuts the power off. A multimeter can check the coil for continuity.
Mullo's, March 2009