sometimes that can be a sign of an ignition system part failing.. i'm not up to speed on the Massimo ignition systems as to if there magneto and flywheel fired, or CDI off of battery.
had a similar issue with a car awhile back, run and get warm and shutoff, wouldn't restart for awhile until cool. turned out to be the ignition coil.
after it dies i would check for spark, either by removing the spark plug and reinstalling the wire and grounding the spark plug against the engine and looking for spark, or by removing the plug and spraying carb/parts cleaner or starting fluid down the plug hole or intake.