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Swingarm refreshing?

Classic Norton Commando Motorcycles.

Swingarm refreshing?

Postby oediehl » Wed Apr 19, 2017 12:51 pm

OK, I'm not sure if soaking in WD-40 helped, but I screwed the nuts back on the cotters partially, and swapped out my plastic mallet for my brass hammer. It took some serious blows, but both the cotters came loose. I then bought a SS 1/2" UNF bolt to screw into the spindle, expecting a serious struggle to extract it, but it slid out easily. Looking at the bushings and the spindle, I would bet money they are fairly new parts. One end of the spindle did not have the larger diameter outer felt ata ll, and the inner felt seemed dry. The other end had both and looked better. I see a little galling on either end of the spindle, but I not so much that I would expect to have so much play in the swingarm. Any thoughts on that?

I suppose I'll play it safe and order all new pieces for a 1975 MK III; I believe I've read that it's not exactly the same as earlier model Commandos, and I wonder if the problem could be that someone installed the wrong parts (even though they seem to fit well enough). What puzzles me is that, with such obvious play in the swingarm (I could grip the rear wheel and feel and see it move a bit when I pushed side to side from the top), I would have expected the bushings/spindle to look a lot worse.

Any shops sell a complete MK3 kit for the bushings/spindle/felts/etc?

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Re: Swingarm refreshing?

Postby L.A.B. » Wed Apr 19, 2017 1:17 pm

oediehl wrote: I suppose I'll play it safe and order all new pieces for a 1975 MK III; I believe I've read that it's not exactly the same as earlier model Commandos, and I wonder if the problem could be that someone installed the wrong parts (even though they seem to fit well enough).


The Mk3 'sealed' pivot assembly has the short spindle with the flats for the cotters and also the shorter length bushes so it's unlikely they are the wrong parts if it all fitted together as the bush in the photos appears to be the Mk3 type.

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oediehl wrote:What puzzles me is that, with such obvious play in the swingarm (I could grip the rear wheel and feel and see it move a bit when I pushed side to side from the top), I would have expected the bushings/spindle to look a lot worse.


Can you be sure you were not mistaking [Edit] Isolastic play for swingarm play?
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Re: Swingarm refreshing?

Postby gjr » Wed Apr 19, 2017 2:21 pm

If the spindle is still a good fit in the bushings I would reassemble the swingarm and keep looking for the source of the play.

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Re: Swingarm refreshing?

Postby oediehl » Wed Apr 19, 2017 2:24 pm

Ah, good suggestion---I had not considered the possibility of isolastic play. I've already adjusted the front, to get rid of excessive vibration around 3000 RPM, but have not messed with the rear. But---would improper isolastic adjustment allow me to manually rock the rear wheel slightly, side to side? I can physically feel the play when I do that.

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Re: Swingarm refreshing?

Postby L.A.B. » Wed Apr 19, 2017 2:41 pm

oediehl wrote:Ah, good suggestion---I had not considered the possibility of isolastic play. I've already adjusted the front, to get rid of excessive vibration around 3000 RPM, but have not messed with the rear. But---would improper isolastic adjustment allow me to manually rock the rear wheel slightly, side to side? I can physically feel the play when I do that.



Yes, it's possible, if the Isolastics are loose or the rubbers have deteriorated.

To check actual swingarm play you need to feel for movement between the swingarm and the cradle at the pivot.
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Re: Swingarm refreshing?

Postby baz » Wed Apr 19, 2017 3:42 pm

those bushes and pin dont look too bad from a photo,as others have said check alo the isolastics but also check the engine to cradle bolts for looseness or ovality, wd40 is not a penetrant use acetone\atf mixed together for best results
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Re: Swingarm refreshing?

Postby oediehl » Wed Apr 19, 2017 4:16 pm

I notice that the rear shocks, if not the springs, may well be vintage---and with the swingarm removed the shocks can be wobbled freely from their upper mounting points. Not just front to rear but also side to side. I imagine that slop could contribute to, or at least not minimize, a loose feeling swingarm?

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Re: Swingarm refreshing?

Postby cyclegeezer » Wed Apr 19, 2017 6:29 pm

oediehl wrote:I notice that the rear shocks, if not the springs, may well be vintage---and with the swingarm removed the shocks can be wobbled freely from their upper mounting points. Not just front to rear but also side to side. I imagine that slop could contribute to, or at least not minimize, a loose feeling swingarm?


They're mounted on rubber bushings, so they should move a bit, but it's possible the bushings are worn. They don't provide much, if any lateral stabilization.
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Re: Swingarm refreshing?

Postby kommando » Thu Apr 20, 2017 12:53 am

I imagine that slop could contribute to, or at least not minimize, a loose feeling swingarm?


No it will not, there is potential misalignment from tolerances and iso adjustments which requires there to be movement in the shocks hence the rubber buffers, as long as the rubber is not deteriorated they will be fine.
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Re: Swingarm refreshing?

Postby oediehl » Thu Apr 20, 2017 12:44 pm

Well, the spindle and bushings look, if not perfect, very lightly worn, and when I put the spindle back through the swingarm bushings I feel pretty much no play at all. So I temporarily remounted the swingarm and dropped the cotters in, and when I rocked the swingarm laterally by hand, I saw a fair bit of movement of the powerplant. So I went to the rear iso mount (I'd previously adjusted the front). I turned the vernier collar the wrong way at first so it's hard to say exactly where I started, but it appeared to me that the iso mount was almost completely loose. So I snugged it in clockwise then backed off 1 1/2 holes, tightened the main bolt back down, and there does now seem to be less motion when I rock the swingarm.

While the front iso assembly looks newish to me, I would guess the rear is not, and since I have the swngarm off already I thought "Why not just replace the iso assembly?". Until I read a bit more in the manual, and realized that with the MK III it sounds like I'd have to drop the entire power plant and tranny. Not this time, I don't think.

So I think I'll just replace the felts and welch plugs, and probably the old shocks, put it all back together to see where I'm at. After I receive the rear brake rotor that I sent off for grinding/drilling. Fingers crossed on the swingarm play!

To replace those welch plugs, do you just drive them in with a properly sized dowel or socket?

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Re: Swingarm refreshing?

Postby Fullauto » Thu Apr 20, 2017 2:20 pm

Wheel bearings?
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Re: Swingarm refreshing?

Postby xbacksideslider » Thu Apr 20, 2017 5:59 pm

An aftermarket head steady will also help control it all.
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Re: Swingarm refreshing?

Postby L.A.B. » Fri Apr 21, 2017 1:20 am

oediehl wrote:While the front iso assembly looks newish to me, I would guess the rear is not, and since I have the swngarm off already I thought "Why not just replace the iso assembly?". Until I read a bit more in the manual, and realized that with the MK III it sounds like I'd have to drop the entire power plant and tranny. Not this time, I don't think.


It can be done without removing the engine (apparently) but it still isn't a '5-minute' job: rear-iso-replacement-t1847.html#p13432



oediehl wrote: So I think I'll just replace the felts and welch plugs, and probably the old shocks,


The original Girling 850 Mk3 lower shock mounting ferrules are wider than the upper mounts (the dimension given for the lower mount ferrule in section F5 of the Mk3 manual is wrong, it should be 0.942"/24mm).
As replacement shocks may not have wider lower mounts so use additional spacer washers to keep the shocks parallel if necessary.

oediehl wrote:To replace those welch plugs, do you just drive them in with a properly sized dowel or socket?


Yes, I've used a 1/2" socket extension bar (male end) but any broad drift should do. Some owners just glue them in with silicone sealant.
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Re: Swingarm refreshing?

Postby The Buckeye Rider » Fri Apr 21, 2017 7:01 pm

To install new welch plugs; insert the plug, it will be slightly loose because it is convex '(' when in position place the rounded end of a ball peen hammer in the center then smack the hammer smartly with another hammer to force it concave ')' it will jam itself in place. I put some sealer on it regardless.
If you've never done these before buy a couple of extras in case, like me, you mess a few up before you get it right.

The rear Isolastic can be replaced without removing the power plant on a MKIII but it takes two men and a boy with lots of leverage to get the job done.
On the same note don't buy the "economy" version Isolastics the good ones are well worth the few extra $.

Speaking from experience on all counts.
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