If it is just tight on the shaft (probably rusted on, as well as deliberately made tight) there is a fairly standard process. First, you put Penetrene on both sides of the boss where it goes over the shaft, and leave it for a day or more (you may need to wet it again occasionally). If you insist on using WD40, make that a few days, or a week or two, whatever it takes. Then get a bolt a bit longer than the original one and screw it into the end of the crankshaft, so when it bottoms in the thread in the crankshaft, its head is about half an inch away from the crankshaft. Center-drill a small recess in the center of the head of that bolt, to locate the pointy end of the screw on a gear puller. Then you can use a gear puller across the back edge of the boss (not across the flat plate on the bottom of the boss, that isn't nearly strong enough). Apply a considerable amount of tension on the puller, then tap the head-end of the puller's screw once with a hammer, tighten up the puller some more, tap the head of its screw again, and proceed that way until it starts to get easier. Then you can partly unscrew the bolt in the end of the crankshaft, and pull it the rest of the way off.
