00 grizzly 600 no spark hot

2000 grizzly 600 .020 over new piston, jetted carb, open k&n filter, cooling fan wired manual
i’ve read through the threads and dont see the issue i have,
i first noticed last winter plowing snow and after some time it would die and not restart until cool "no spark", this last weekend we took my grizz and wife’s polaris to the hills I first took the grizz up to check out the area, come back down got the wife doubled up to show she could do it also, on the way back I turned on the fan was running hot and later the grizz died and had to tow it back would not restart till next morning, just loaded back up and used polaris all weekend.
my issue after runs at a heated temp for a short time i have no spark. could the stator be breaking down hot ? im also thinking adding a 2nd fan blowing on jug for slower trail rides, my grizz runs great other wise on short rides around our 2 acres