How to square up MK3 crank and g'box shafts

I have had a belt drive system on my MK3 Commando for the last two years, with no apparent issues, or so I thought :!: When I have come to fit my new needle roller bearing (with the rubber seal on it) I have discovered that the belt is not running true as the two shafts are not squared up, and that it has caused some wear on the outer side retaining plate on the front pulley and also worn a few millimetres off that edge of the belt.

Without this plate fitted on the crankshaft pulley (the outer plate) the belt will start running off the pulley and be well on the way off after 50 revolutions.

As a lot of you will know, there is no adjustment for the MK3 gearbox. A friend of mine who has had the same problem took the subframe out, bolted the engine to it, and fitted the gearbox and then clamped the front engine in a bench vice, and got his "subtantial" son to "lean" on the appropriate side of the engine plate until it had squared the gearbox shaft up with the crankshaft.

I can't really see any other options than the above, but before I reluctantly pull the engine out and lean on my subframe, does anybody else have any ideas :?:

Reggie,
Before you start pulling it all to bits are you sure the belt wasn't too tight, then check the sleeve gear bushes aren't worn.

Cash

Thanks for the suggestions Cash. The belt's tension is OK, and I can't feel any play on the clutch when rocking it on the shaft, and so assume that the sleeve gear bushes are OK.

Also, the belt is running off to the left when sat on the bike looking down at the pulley, which to me suggests that the centres are getting wider.

Just out of interest, the plates were new from Andover two years ago.

Hi Reggie,
before I needed to upgrade to Maney crankcases, I used Mk3 ones. Two sets were almost new when I go them, but I still spent a day on the mill squaring them up. The problem was that the main bearings weren't lining up properly with each other (yes, they were matched cases) and also the engine mounting holes in the back of the cases were on the piss too!! Quality control wasn't too good in the final days of Norton unfortunately! It might be worth getting the cases checked out, and maybe slightly oversize mounting bolts reamed square to the crank. If you do go down that route, make sure you remove the 2 large dowels between the cases and ream them separately.!

Interesting Seely.
I'd never thought about the cases/case mounting holes being out of true

I unfortunately don't have a lathe. Do you have any recommendations as to whom may do this work, were I to go down this route :?:

Thanks Ludwig, in the notes from Norvil, they do state that the bottom gearbox stud hole can wear "oval" if it has been run with this stud left loose. I had read this, but I was thinking that the effect of the plates pressing on the shoulders of the stud holes when tightened fully would have squared things up. Thinking about it now, I suppose that the twisting effect can wear the shoulders out of square.

Thanks everybody, you've pointed out a few things to examine/consider that I hadn't thought of. It's beginning to look as if the engine and engine plates will be coming out for examination. Oh deep joy. :cry: