first thing i'd suspect is the idle was not adjusted on a hot engine..
if both idle air and idle speed adjustments are available, go through the routine..
Get the bike engine good and hot.
Set the lowest idle speed possible (speed screw) ..till the engine threatens to die.
Play with idle-air (air screw) so that idle speed increases.
Again, lower idle speed to nearly dying.. And again play with the air to increase rpm..
Repeat speed and idle air adjustments until further idle-air adjustment won't increase rpm anymore.. You're done.
Otherwise you might have some mild piston seizure or something.. lots of friction when hot .. But if it will immediately start right up again without cooling off, this wouldn't be the trouble.