Now that the chain is off, try and spin the axle. Does it spin freely? Did your engine possibly move and tighten the chain a lot? If not, check your rear bearings. Probably not it, but put the starter nut back on the shaft and try to wheel it around either by hand or with the 17mm socket to check for compression/stuck piston. I don’t see how that would lock up the axle, but it’s something to check for. If everything checks out, clean bearing and all surfaces with brake clean and grease the bearing. Make sure you pay attention to what way those washers face when being installed. One is coned(clutch side) and the other is stepped (between drum and starter nut). Once back on see how it spins.
Is it the MY 07 (Red/Green button Electronic Box)or 09 (Key Start) engine?
Give this a good read and see if this helps with greasing the bearing, torque specs and chain tension.
Tony Kart / Leopard
November 15-19, 2017
Las Vegas, Nevada
SKUSA SuperNationals 21
2018 Events TBA