viewtopic.php?f=10&t=4449Have a look at this topic or do a Search on warm starting, it crops up regularly.
I had big warm starting issues because of spit back, just learned to cope with it by switching the fuel off and keeping the scoot running for a few mins before shutting it down. Starting it without fuel on and if that failed pulling the air hose off getting it running then putting it all back together.
I don't beleive mine was caused by any one issue, I think it was a combination of the carb/timing/piston-barrel-head wernt right. Yours may be different.
I only completly cured my problems by fitting a modern cylinder kit and a 30mm delly, starts first or second kick now.