Mysterious starting-problems

an IMPORTANT question: ive a big problem with my vespa 50 (105[;)] special. it runs very good but when the engine stops running for 5 minutes or so it doesnt run anymore. then i have to take the sparkplug out and in and then i have to push it 50-100(!!!)metres till it runs. but i get an excellent spark and fuel supply is o.k. but engine is completely new! THIS SUCKS!!! please help me or i`ll throw it away and buy a DERBI!!![:@]
thank you Georg[?[]

I sounds like you could have either a problem with piston rings being the wrong size. How old is this engine, does it have points on it or is it powered by a stator? If it is points then im afraid that by all accounts youll just have to live with it. Sorry [:’(]