Generally it is a bad idea to fit a watercooled engine piston into an aircoled engine.
The car pistons are generally lighter and have less ovality than bike ones.
You might get away with it on a bike you run lightly but don't be suprised if the crown splits off or you get excessive piston slap.
OTOH deisel pistons can take it but you need to do a reasonable amount of machining.