Swing arm spindle & cradle

Hi, I feel I should apologise straight away for asking this as it seems to have been brought up many times before....
I have a 1970 750 and upon stripping it down have found the following:
-One of the bushes is loose in swing arm, you can easily pull it out. Other side needed to be pressed out. When I swapped them over, nothing changed, so the bore of the swing arm has worn somehow. I can get a 0.05mm (2 thou) feeler gauge in between. Can I use Loctite (603 I think), or does the interference fit of the bush improve the bush fit on the spindle? If the latter is true, then I'm knackered? Maybe I could knurl the OD of the bush (not sure how I'll do this!) to improve the fit?
-The spindle is loose in the cradle, and I think I'm passed the o/size spindle size, but I'll check again tonight. The spindle bore appears to be oval and I can get a 0.10mm (4 thou) feeler gauge in between at one point. If I can find a Mk3 cradle will that be the best thing to do? I'm not convinced the fixing collars/ welded nuts will solve my particular problem.
Thanks very much for your help

if the swingarm was in a static position all the time and didnt cop a flogging then the Loctite might work and it might not, not much help eh..

Nobby said:

One of the bushes is loose in swing arm, you can easily pull it out. Other side needed to be pressed out. When I swapped them over, nothing changed, so the bore of the swing arm has worn somehow.

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One possible explanation is that sometime in the past a bush seized on the spindle possibly due to a lack of lubrication and then began turning inside the swinging arm, causing the apparent slack fit between the bush and swing arm tube.

Nobby said:

-The spindle is loose in the cradle, and I think I'm passed the o/size spindle size, but I'll check again tonight. The spindle bore appears to be oval and I can get a 0.10mm (4 thou) feeler gauge in between at one point. If I can find a Mk3 cradle will that be the best thing to do? I'm not convinced the fixing collars/ welded nuts will solve my particular problem.

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From past discussions the (Kegler)collar or bolts/nuts modification appears to be an effective answer to any loose spindle problem.
If you do find a MkIII cradle then it will need to be modified so the gearbox can be moved for primary chain adjustment.

Thanks, that helps (a bit!)
Has anyone else had a problem with a loose bush in the swing arm?
At the moment that seems to be my main concern

You can always have oversize bushings made, but you might need to buy a batch of 10 or 20 for it to be cost effective. Of course the swingarm would need to be precision bored to match. After all that, the price of a simple e-bay replacement swingarm looks quite nice!

How loose are they?
I would think the a loctite product or even JB would work as long as the fit is not sloppy.

Upon applying adhesive, I would mock up the swing arm in the cradle with the spindle running through it. Move the swing arm up and down every few hours to validate functionality.

Otherwise, maybe start looking for a new/used swing arm.

Were it my problem I would get myself some brass shim stock, or maybe I would just cut up a beer can. I would cut it into strips that I could fold over the edge of the swing arm tube. My goal would be to estimate how many I really needed to make it a good interference fit when I pushed the bush into the tube. By folding them over the edge of the tube, it would be hoped that they might stay in place rather than being driven out when I pushed in the bush.

I do think the tight fit of the bush helps achieve the correct fit for the spindle. But I don't have a lot of experience with it. Just an observation. a little tight on the spindle is probably better than loose in the long run.

Russ

I just remembered I've run into too loose or too tight bushes that turned out only to be the bushes or their bores out of round and some good smacking around bore surroundings or the bush over its shaft got the clearances round and right. MIght just put the bush and spindle in and bang and bang till working frustration out or getting a great fit work hardened to stay that way. Could JBW the innards then once hard set up with heat helping have it line bored to suit.

Your bike might have been laid over at some point and swing arms often show it most. Just a thought. I bought a new one from Rabers for similar reasons and had it modified right away.

The existing bushes seem a very good fit on the spindle when out of the arm, and I wouldn't think it should be much tighter. So I'm not convinced that the fit improves when the bushes are in the swing arm. Plus it can only be better with new bushes and spindle!
So, I'm going to try Loctite with one of the old bushes in the swing arm and see how it holds as a trial. It's not a sloppy fit and probably less than can be taken out with shims. Might also try a little banging.....
As to the cradle, will most likely get a new one from Andover as they do a Mk3 version with the adjusting slots for the primary drive tension.
So that's one problem sorted....

Thanks!

Nobby said:

The existing bushes seem a very good fit on the spindle when out of the arm, and I wouldn't think it should be much tighter. So I'm not convinced that the fit improves when the bushes are in the swing arm. Plus it can only be better with new bushes and spindle!
So, I'm going to try Loctite with one of the old bushes in the swing arm and see how it holds as a trial. It's not a sloppy fit and probably less than can be taken out with shims. Might also try a little banging.....
As to the cradle, will most likely get a new one from Andover as they do a Mk3 version with the adjusting slots for the primary drive tension.
So that's one problem sorted....

Thanks!

Click to expand...

Sometimes I'll sacrafice a blade from the feeler gage set to get a just right shim for what your doing. And i'll use some loctite with it. If I was doing this on say a layshaft bearing I 'd stake around the edge to try and keep the shim from ever coming out and getting chewed up.

This stuff should solve your problem:
https://jdparts.deere.com/partsmkt/docu ... tm#loctite