Basically if they're stuck on badly it's a pain, it can take a good few hours to get it all off. I don't know why some stick that badly, maybe some idiots are using some kind of instant gasket as well.

The cases can be even worse if the motor is in the bike.

I coat the gasket with a smear of grease, it stops them sticking at all and I've never had one leak yet.
_________________
Please do not PM me technical questions, if you can't find it on the Forum start a thread