wont run when hot after stalling

[bean2080]

when ever my quad gets hot (very hot) like the second hour durring XC races it always wants to shut off for some reason and then it wont start. its not steam or anything from water, its just at random times. my quad is a kicker and does have the hot start and about 95% of the time the hot start works great but sometimes it seems that it dont help at all so therefor my quad wont start. now if i just leave it set for a couple minutes then it will fire up again but who wants to set and wait for it to start when your in a race lol
i do not have a temp light and my fan is not wired to run all the time, it just runs when its hot. if anyone has any ideas what could be wrong it would be great.
thanks

[DnB_racing]

valve clearance

[bean2080]

i just shimmed the valves to specs this last weekend. that shouldnt be the problem.

[fastredrider44]

Check it again. Also check compression.