I'm trying to replace the pto clutch on my Craftsman DYT 4000. I can't get the bolt to move without moving the crankshaft as well... the mower's front wheels are in the air right now, so if I put it on ramps to work on it instead, will that keep the engine from moving? If not, how can I loosen this bolt? Thanks!

There is actually a trick that can be used in this situation if you have no means of wedgeing something somewhere like you would for a law mower blade.

Here is the trick. Stuff a rag into the spark plug hole. You should not need much. Use a rag that won't tear easy. The piston will hit against the rag.

Impact wrenches work too.