Before you get in a big hurry and assemble your flywheels, always (always) be certain your drive gear(belt or chain) fits the splines of your sprocket shaft. I've seen a lot that didn't fit, or were very tight. It's a bitch to be messin' with this after your motor's all assembled. You just might have to service this thing out-on-the-road somewhere - and you'll be screwed if you can't get it off (on back on) with no air tools or fancy pullers. Upon initial inspection, it started on the splines(barely) and I supported the shaft and pressed it on(carefully) and pulled it off. Then deburred the burrs. I did this a few times until I have a nice press fit - and I can remove it with my "tool kit" puller.