Put a short 3mm bolt in the end of the crankshaft, and thread it all the way in. This way you don't ruin the tip of your crank. Then use the puller. The screw should just turn right out. You can place a wrench, or some other flat fork behind the flywheel for support, and hammer it loose. But just remember, your crankshaft will be pounding the inside of your backplate. It's a good idea to remove the backplate if you use this method.