Whilst putting the engine back together remember to put the rear mounting studs (3 off) in place in the rear of the gearbox housing before joining the crankcases as they wont go in afterwards. Also, if you have the rear chain cover (black plate that fits behind the gearbox sprocket area, that keeps road grit and muck from getting behind the primary chaincase) fit that before plonking the engine in the frame as its nigh on impossible to fit afterwards. That's why you dont see them on there very often.
Chris