i presume it not cranking over very well when hot.
when it's hot disconnect the king lead that goes to the dizzy and cranck it over, if it spins over much better, your ignition timeing is out FACT
it's slightly over advanced you need to loosten the nuts on the dissy and set it up with a timeing light. the ignition timeing is diffrent to the timeing between the cranck and the cams and the inter cam timing, it has it's own adjustment and is rather a lot more sensitive just fitting a new cam belt can throw it off