Poor starting

I own a 1980 p125x vespa it starts ok when cold but when warm it is a right pig to start. I have tried turning the fuel tap off just in case of flooding no joy can any one Give me some ideas.
p.s It has no Mods all standard.

Put in a new silver spark plug (bosch) which i found always to help a poor starter.[:D]

Get some carb cleaner and clean all the jets.