Put your thum over the spark plug hole and pull the engin over you will feel the compresion. with the spark plug in put your hand over the exust you should feel air blowen out when the engine is turned over this will tell you that your valves are working more or less corectly. Then the only thing left is your spark timing. I do not know exactly how it is set up on this motor but have a look and see if there is any sign of the flywheel faving slipped this will cause you to have good spark but not at the right time.
hail, December 2004