Rear Wheel Assembly Dimensions

Rich_j · Apr 18, 2011

Does anyone have dimensions for the rear wheel and its spacers for an 850 Mk2a.

The whole assembly of wheel/brake/spacers etc is a real squeeze into the swingarm, how wide should it be?
Also the chain runs very close to the left side of the chainguard and occasionally makes contact.

I've got a full set of aftermarket stainless kit in the rear wheel and am suspicious something isn't quite right.

Cheers

Rich

swooshdave · Apr 18, 2011

Rich_j said:
Does anyone have dimensions for the rear wheel and its spacers for an 850 Mk2a.

The whole assembly of wheel/brake/spacers etc is a real squeeze into the swingarm, how wide should it be?
Also the chain runs very close to the left side of the chainguard and occasionally makes contact.

I've got a full set of aftermarket stainless kit in the rear wheel and am suspicious something isn't quite right.

Cheers

Rich

Sounds about right. Pry the spacer in next to the speedo then grab the chainguard and tweak as for as you can. At least that's what I did.

Diablouph · Apr 18, 2011

I had the same problem on mine. I finally left out the spacer (#34 NM13270) next to the Speedo Gearbox. Not that I am suggesting you do that, I just could not get the thing in.

Boy are you right, the chain is VERY close, and I can't see any reasonable way to fix it.

Also, one of the muffler mounting bolts (#32, left side) was hitting the swing arm. I had to shim it out with washers.

Flo · Apr 18, 2011

Just been through all that.
For years I did not have the top hat spacer in the speedo gearbox, now that I have, it is difficult to get the wheel in. It is difficult to get the cush drive fully located to get the spacers in, but it is correct.
If you have put an aftermarket stainless chaingaurd on, the chain will be to the left quite badly. I can't understand why pattern manufactures go to all that trouble to make a pretty chaingaurd, then bollocks it all up by making the bracket too bloody deep. If you look at the original chainguard, the bracket is quite shallow & is quite difficult to get a spanner in there.
I've managed to flatten mine to correct depth & got the chain in the middle.

ML · Apr 18, 2011

Make sure the bearing spacer in the hub is the correct way in. The long nose end goes to the speedo side. Its not uncommon for it to be installed wrong way in and what that does is to protrude too much out on the brake hub side. Use the front wheel axle as the drift into the spacer. It's the official tool!

Micj

swooshdave · Apr 18, 2011

Diablouph said:
I had the same problem on mine. I finally left out the spacer (#34 NM13270) next to the Speedo Gearbox. Not that I am suggesting you do that, I just could not get the thing in.

You need to bend your swingarm more. :mrgreen:

DogT · Apr 18, 2011

The early models had the same issue. On my 69, the chainguard is contacting the left side shock. I had to make a special spanner go get into the space in the chainguard bracket to hold it. The chain is very close to the guard and my original one was eaten up mostly by the chain. I think the best you can do is keep things away from the chain as best you can and don't let things get loose and replace things as they wear out, certainly don't let the drive chain get loose. I certainly would not eliminate the top hat spacer in the speedo gearbox, that's a surefire recipe to ruin the gearbox.

The bearing spacer if placed in the wrong way, you cannot fit the rear wheel correctly, things will lock up upon tightening, you can ask me how I know.

Dave
69S

Flo · Apr 18, 2011

ML said:
Make sure the bearing spacer in the hub is the correct way in. The long nose end goes to the speedo side. Its not uncommon for it to be installed wrong way in and what that does is to protrude too much out on the brake hub side. Use the front wheel axle as the drift into the spacer. It's the official tool!

Micj

If the short end was at the speedo drive end, wouldn't the speedo drive rub against the wheel?

(I got arrested once, my s had fallen off of my speedo)

Diablouph · Apr 18, 2011

I certainly would not eliminate the top hat spacer in the speedo gearbox, that's a surefire recipe to ruin the gearbox.

I didn't need to hear that. Is the spacer flat, or does it have a lip? The one I took off was flat.

DogT · Apr 18, 2011

I have special notes in my Workshop manual to indicate the short and long ends of the rear wheel bearing spacer. The short end goes to the LS and the long side goes to the RS. For some reason it's counter intuitive, but that's the way it worked for me. It wouldn't work the other way. Item 29 here http://www.oldbritts.com/1971_g16.html. The 850 may be different, I don't know.

Look at item 34, it is the top hat spacer and looks like the picture, definitely a lip. I had a thread on the gearbox quite a while ago, I'll look it up if you need.

Dave
69S

Diablouph · Apr 18, 2011

Look at item 34, it is the top hat spacer and looks like the picture, definitely a lip. I had a thread on the gearbox quite a while ago, I'll look it up if you need.

Thank god, I thought there was another spacer in there. I have that one (#34) in. I just thought it was part of the drive.

rick in seattle · Apr 18, 2011

Two years ago I spent an agonizing four days assembling the rear wheel on to my rebuilt Mk3. This was an interactive process involving both Les and 79x100, who were out in their garages at midnight GMT taking measurements to help me out (gentlemen, if you're ever near Seattle, the drinks are on me). The process is contained in the post

mounting-the-rear-wheel-the-mk3-t3692.html

The short of it all was that my swingarm separation measured 8.0 inches at the rear paddles, 1/8" under what both Les and 79x100 measured. It took a large crowbar to spread the swingarm enough to accept the wheel. Once mounted, the wheel tracking was fine. But that wheel is NEVER coming off.

Good luck.

Rick

Diablouph · Apr 18, 2011

It took a large crowbar to spread the swingarm enough to accept the wheel.

Wasn't a "large crowbar" part of the original tool kit?

swooshdave · Apr 18, 2011

Diablouph said:
It took a large crowbar to spread the swingarm enough to accept the wheel.

Click to expand...

Wasn't a "large crowbar" part of the original tool kit?

Right next to the hammer.

Rich_j · Apr 21, 2011

Forgot I'd started this one.

Anyway got a bit side tracked for a while there but back on the case now.

The brake drum bearing was feeling a bit rough so I decided to knock it out which gave the opportunity to assemble all the parts without the drum and all the extra seal parts.
It was a lot easier getting the big spacer in like this. Measuring up the, the spacer was only .075" bigger than the gap, unfortunately I didn't take any before measurements.
Looking at the drum and wheel it looks like the cush rubbers may be stopping the two from seating properly. Putting the drum back in without seals and cush rubbers the chain run looks a bit better.

I'm going to by new rubbers and take the thickness of the top hat washer for the speedo drive off the large spacer and see how that goes.

swooshdave · Apr 21, 2011

Rich_j said:
I'm going to by new rubbers and take the thickness of the top hat washer for the speedo drive off the large spacer and see how that goes.

I wouldn't take anything off the spacer until you have properly sorted the cush rubbers.

Diablouph · Apr 21, 2011

I wouldn't take anything off the spacer until you have properly sorted the cush rubbers.

Goooooooooooood point. The seating of the rubbers about drove me crazy.

Rich_j · Apr 22, 2011

Diablouph said:
I wouldn't take anything off the spacer until you have properly sorted the cush rubbers.

Click to expand...

Goooooooooooood point. The seating of the rubbers about drove me crazy.

Never done this before, am I about to enter a world of pain again?

Any tips?

Rear Wheel Assembly Dimensions

Similar threads