Hi Bob,
What is the model?
I would check a few things
Scooters have automatic cut out side stand switches that cut the bike out if side stand is down. I have never heard of one for the centre stand but it is worth a look to see if for what ever reason the side stand one has stuck on or is faulty, if you have a side stand. Make sure it is moving freely.
I would also adjust the idle speed on the carb and make the bike rev higher. Does this make a differance?
I would suspect the auto clutch has siezed or locked up and needs replacement.
bb
December 2009