Poulan 2150 LE Chainsaw

I have a Poulan chainsaw that is extremely hard to start and won't run when hot. It also 'looses' fuel but is not leaking externally. When hot I have noticed fuel 'percolating' into the carb from the tank hoses. Ever heard of this? Can the case be cracked or a gasket leaking? Can fuel leak from the carb to the crankcase?