Some people have luck getting them off by undoing the nut and applying gentle pressure with a bit of patience. I am rarely gentle and rarely have a lot of patience so I use a puller like this:

[Linked Image]
[Linked Image]


My puller is home made but works very well, it threads into the 3 holes around the main nut and with the center nut removed, the big bolt on this puller pushes o the crankshaft and heaves it off. You do need to be careful as I have managed to buckle one crank before form the flywheel being so tight, sometimes leaving the center nut on but loose to get it started is a good idea.