Gearbox top bolt spacer?

I have a 1974 Mk2A 850 Commando. I'm rebuilding it and it wasn't really done right last time round. I'm wondering if some one can tell me about the gearbox top bolt 'spacer' – does it go between the gearbox shell and the frame/cradle? That would make sense... except mine didn't have one there (it was 'outside' the frame, so between the top bolt nut and the cradle) and now that I've got the correct spacer I can't see how it'd actually fit in there between the shell and the frame/cradle anyway?

Any advice greatly appreciated!

Headfullofsnakes said:

I have a 1974 Mk2A 850 Commando. I'm rebuilding it and it wasn't really done right last time round. I'm wondering if some one can tell me about the gearbox top bolt 'spacer' – does it go between the gearbox shell and the frame/cradle?

Click to expand...

Yes

Headfullofsnakes said:

That would make sense... except mine didn't have one there (it was 'outside' the frame, so between the top bolt nut and the cradle) and now that I've got the correct spacer I can't see how it'd actually fit in there between the shell and the frame/cradle anyway?

Click to expand...

If the top mounting has been tightened without the spacer in position then it has probably bent the cradle in towards the gearbox.

Oh right. Bugger. How's that best fixed then?

It just occurred to me to mention that this gearbox shell is new and hasn't been in the bike before. I got the shell from Norvil... any chance they make them to fit the cradle 'without' the spacer? There's no way this spacer's gonna fit and I'm pretty sure the cradle's not bent? Have a friend coming over tomorrow who can give me good measurements though... my calipers won't fit in some of the right places.

Headfullofsnakes said:

It just occurred to me to mention that this gearbox shell is new and hasn't been in the bike before. I got the shell from Norvil... any chance they make them to fit the cradle 'without' the spacer? There's no way this spacer's gonna fit and I'm pretty sure the cradle's not bent? Have a friend coming over tomorrow who can give me good measurements though... my calipers won't fit in some of the right places.

Click to expand...

If your gearbox cradle isn't bent, and totally parallel, and there's no gap (from memory it should be 1/8"?) then it's possible that you've been sold a Manx shell - it happened to me
You can tell by the way the top lug is machined - if the boss stands proud from the case it's for a Manx - if the boss is machined such that it's flush with the case, then the problem's elsewhere.
Unfortunately a certain supplier has been mentioned...

This is what it should look like

No biggie - I ran an Atlas shell in Ms Peel w/o the stupid spacer notch so cradle just clamped on the full length flat of the top boss. For some stupid reason Norton thought the stupid space was a good idea to make moving the shell in the cradle easier, instead of adding sloppy handling of shell in cradle then the beating bashing swearing to get the stupid spacer aligned. I doubt the cradle is bowed to matter as pretty springy up there, so if ya can squeeze in the shell w/o the spacer then good to gogo.

If cradle bowed not to accept the new shell fairly easy then might try a spreader to bow back out some or I'd grind the dang shell boss to fit decently and then forgetaboutit till next time tranny needs service. If not adaptable while in frame then may have to break bike in half to get cradle back in shape. BTW when shopping world wide for replacement shell I found that this extra notch feature costs like $250 more than shells w/o it, a decade ago.

The shell is correct, so all good from Norvil's end. The cradle is bowed slightly – about 2mm. Will try a spreader of some sort and see if I can get that spacer in there... I've had a lot of gearbox and primary trouble and I'd like to get it all hunky dory!

Let us know how you make out with it. Mine is the same. This must've happened the only time my bike was in a real bike shop when I was 22 so it has been that way for almost 40 years. I saw a picture on this forum on how it is supposed to be and now it is on my winter list to fix. I think a big pry bar would take care of it. That is my plan anyway.

Russ

Managed to get it in there! Removed primary inner, loosened everything off around the cradle and managed to jimmy it into position.