Seems bit of a pity I have to pull the whole thing apart again just to get the gearbox out... still practice makes perfect I guess.
I think there is ample evidence of skullduggery to justify it though. To be honest, the gearbox is the weak link in the whole build as I haven't done too much to it compared to the motor what with new this, that and everything in between. So will replace all bushes and bearings. Already got new kickstart quadrant and ratchet, cam-plate, layshaft, thrust washers and drive sprocket. The gear clusters looked alright, so will leave them alone.