Let me expand on this somewhat, most harmonic balancer pullers will not work directly to pull off a 650SX flywheel, make sure the inner shaft of the puller is small enough that it contacts the crankshaft. Like I said most are not so what you do is find a nut, or spacer that will fit inside the flywheel and contact the crankshaft, otherwise you are just screwing the puller bolt against the flywheel itself and it will never come off that way.
Once you have the puller bolt tightened down, remove the socket or wrench and rap the puller bolt with a hammer, tighten down the bolt again and repeat till it come off, you can also heat the inner hub of the flywheel with a propane torch to aid removal of the flywheel.