Odd nuts hitting swing arm

Hi all, usual story of long time lurker, first time poster etc. I'm planning to throw up a build thread for my 74 850 Roadster "freshening up" (read: it's in many pieces on my garage floor at the moment), but in the process of dismantling it, I've found something I wanted to ask a question about first.

If you have a look at this photograph of the engine cradle, you'll see two nuts welded onto the swing arm pivot. These had cap screws partially threaded in that were making divots into the swing arm. I can't find a reference to any device on any of the exploded diagrams at my disposal, so if it's not something from the factory, why would you perform such a modification, it just seems to be damaging the swing arm? I'm curious before I go to the trouble of removing said nuts and patching up the pivot.



Thanks in advance,
Chris

a couple of bolts in them tightened against the Swingarm shaft stops it from rattling around in the cradle,
a popular mod

madass140 said:

a couple of bolts in them tightened against the Swingarm shaft stops it from rattling around in the cradle,
a popular mod

Click to expand...

Yeah, but not nuts that big!

previous owner didnt want that spindle to move and maybe he was going for rigid rear end with the bolts stopping swing arm movement.

hi. 40 years ago when I bought my 1971 750, I had an oversize swing arm pin [ king pin ] made, and wound it in with a austin mini suspension puller. its never going to come loose now. I am a car mechanic, and it made me laugh when the instruction manual said that shaft was an easy slide fit. What idiots they were to say that. If a king pin on and early car or truck had a king pin that loose it would flog out in no time. Norton did come up with some shoddy ideas when they built these bikes, but obviously i have dealt with them for a long time. the first mod I did was to throw the side stand as far away far from the bike as i could as it was a design nightmare that was not worth fixing.

Cool, thanks guys. Looks like I have a couple of options then... Turn up a new pin and patch the shaft (probably more expensive even with a machinist in the family) or just fit some shorter button head screws so they don't hit the swing arm anymore.

You could probably get away with grinding off some of the thickness of each of the nuts (to get the bolt head in tighter) and you could probably grind some off of the bolt head too. just a thought, anyway welcome and thanks for the post, I look forward to your build thread. Cj

Grub screws..

Could you post a picture with the swinging arm and pivot in place?

Is the pivot a 850 MKIII type , with 2 flats ?

As noted, it is a good mod (or a pair of swingarm clamps to serve the same purpose) so don't remove the nuts. As also noted, shorter bolts/grub screws will correct the rubbing and retain the firm clamping of the swingarm spindle. 850 handling can improve noticeably with that mod so it's well worth having.

Maverick said:

Cool, thanks guys. Looks like I have a couple of options then... Turn up a new pin and patch the shaft (probably more expensive even with a machinist in the family) or just fit some shorter button head screws so they don't hit the swing arm anymore.

Click to expand...

Here's how it should work out as a modified Mk2 swing arm. The new swing arm pin is a Mk3 .005" oversize. The Mk3 has 2 flats 1" either side of the centre. The Mk3 swing arm tube had cotter pins as standard. The centre fixing bolt has been converted to a oil top up feed.