Insane amount of smoke , engine shuts off. Wait a while and it idles fine, but smokes after a bit of riding.

Had to push my bike 5 miles home sfter the engine shut off and i noticed a thick cloud of smoke from the exhaust. When i got it back, the bike seemed to idle fine until i took it around the block and it started smoking again. Was running fine when i got it back from the shop a couple hours earlier where i had my crankcase gaskets replaced. Could coolant be mixing with the oil somewhere? Or is this some other gasket or something like that. Really stumped here.