Motorcycle Repair: Vespa p200, fuel air mixture, insufficient lubrication

Question
I have a p200 that I can get started but when riding it seizes.  It is a soft seize because I can get it started again, but I do not know why it will seize.  I think I hear a knocking by the cylinder but I am not sure if that is normal or bad.

Answer
Tom,
Check your timing to be sure, if it's drasticly off you can experience preignition which can suddenly stall or "wet sieze" an engine.  Check your points, they may need to be set and/or replaced.  Also, very important that your fuel to oil ratio is correct if you are premixing.  If there is an oil pump you may have a problem with oil delivery, a clog, misset pump, broken pump.  Do not run the motor until you are sure you are getting enough oil into the carburator.  If your scooter uses a autolube oil pump system and you are unsure about it's effectivness you may pre mix.  Also, make sure your Fuel/air mixture screw is 1 and 1/2 turns out from seated and that your floats in your carb. are set at the correct hight.  Insufficient lubrication is the most commen reason for any type of engine siezure.

Mike