It's been a long time since I built a two stroke and at present I'm putting together a 250cc single engine and I can't remember how easily the crankshaft should rotate after putting the cases together with the oil seals in place. I have a Ducati single engine that the crank will always rotate to it's natural position if located away from it and just let go. Should a two stroke engine do the same, bearing in mind the drag/friction from the crank seals? The engine I have have isn't doing this and does feel a little tight.
You will feel the oil seals but it shouldn't be tight. Is it a vertically or horizontally split case? It can be a very common to disturb the crank truing when installing a crank in vertically split cases.
Vertically split. I'm going to measure everything again to make sure I haven't over shimmed it causing it to bind up. Failing that I have thought that it might have gone out of true, I did have to tap the main bearings onto the crankshaft and also tap the crank into one half of the cases. I rebuilt this engine multiple times years ago and never had this problem before.
Doesn't matter if your tapping caused seals to bind (doubt it), you've ruined any "true" you may have dialed in on the crankshaft. It's gonna run like shit and quite possibly grenade. Start over. Press the bearings and case halves onto the newly dialed-in and properly supported* crankshaft. I can only assume these are new seals but, if not, wtf? *
