Overheating Scooter

[lwa99bgp]

My 50cc Suzuki scooter seems to have a problem in the cooling system. Pressure appears to have built up and popped the cap off the coolant tank and threaded it in the process. I did replace it with a new one but the same thing has happened again.

Any ideas what could be causing this build up of pressure?

[markja]

possibly the head gasket has gone and is allowing the combustion chamber to over presure the cooling system.
take the rad cap off, fill to the brim with water, leave rad cap off and run engine . if water pours out at a great rate then bubbles appear; head gasket is main suspect.
don't use it on road untill it's sorted as you may do big damage to the engine.