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Swing Arm Bushing Help

Posted By: Doug F

Swing Arm Bushing Help - 05/17/19 6:42 pm

Hi All, Finally getting the frame together On my A65 build , the swing arm bushing seems frozen to me. So when I install the swing arm into the frame & tighten it , the ends of the bushings are rubbing & working into the frame plates when the the swing arm pivots. Haven't had any luck finding any info. about this anywhere. just info. about bushing removal etc...
Can anyone tell me how much movement the silent block rubber should allow I'm worried that as the suspension gets work it's going to work holes into the frame on either end of the swing arm.
Was thinking about fitting a thin washer on the ends to protect the frame ? Also if I do work the old bushings out ther's no mention of where to get or how to install new rubber as it certainly is destroyed in the removal process.
Any help is always much appreciated
Thanks.
Posted By: Allan Gill

Re: Swing Arm Bushing Help - 05/17/19 6:56 pm

What’s rubbing the outer or the inner cage? The inner cage should clamp between the frame, when tightened movement by hand would be difficult. Because of this you should really preload the suspension before tightening the nut. ie, have the bike complete, have someone sit on the bike with the front brake on whilst you tighten it.
Posted By: Doug F

Re: Swing Arm Bushing Help - 05/17/19 7:23 pm

Thanks for reply Allan
The ends of the inner bushing protrude & seat against the inner frame . When I tightened the nut & check to see how it pivots I can see the bushing moving along with the swing arm. So I took it back off & sure enough There are wear marks in the frame from pivoting the swing arm up & down aprox. an inch or so. My manual shows no torque spec. for the swing arm nut.
Installed the spindle off the frame using a spacer to seat up against the ends of the bushing & tightened up the nut pretty tight to see how much movement I get before the bush starts to rotate along with the spindle. Looks like maybe 1/8" - 1/4" at best
Posted By: Doug F

Re: Swing Arm Bushing Help - 05/17/19 7:31 pm

Sorry I worded that wrong
1/8"-1/4" movement of the bush inside the swing arm so any more than that & it will rotate along with the swing arm & rub into the frame
Posted By: Allan Gill

Re: Swing Arm Bushing Help - 05/17/19 7:35 pm

Usually they are a brush fit when putting into the frame, you don’t really want to be tightening any part of the frame to the point where your “pulling the frame in” this would create a guitar string effect and will amplify any vibration may even induce fracture but this isn’t something I have seen. The guitar string effect is same when mounting the engine, it should be shimmer into the frame with distance pieces or washers. I’m not sure of the sizes but possibly some thick crank shims on each side of the swingarm will provide the sufficient packing required. But yes that inner sleeve wants to be locked tight against the frame plate.
Posted By: Allan Gill

Re: Swing Arm Bushing Help - 05/17/19 7:40 pm

Originally Posted by Doug F
Sorry I worded that wrong
1/8"-1/4" movement of the bush inside the swing arm so any more than that & it will rotate along with the swing arm & rub into the frame


I’ll retain the last message in case I misunderstood at all. If the inner cage is clamped tight (and you haven’t had to pull the frame to do it) then you will get some movement from the swingarm up or down, you shouldn’t get any lateral movement (side to side) from the swing arm, the arm will move as mentioned but will try and return to its start position, it’s not too dissimilar from winding up an elastic band on one of those airfix toy aircraft. Hence tightening the spindle when the bike is preloaded.
Posted By: Doug F

Re: Swing Arm Bushing Help - 05/17/19 8:36 pm

Thanks, No side play noticeable. feels secure only very minute pulling of the frame to tighten. for now anyway My fear is that after it's all together as I ride & work the suspension that pivoting of the inner bush
against the frame will wear into it & create end play & weaken as well. I get the damping effect of the rubber but it seems like it should allow for more movement & the bush should not move on the spindle
thus rubbing into the frame but that the swing arm should pivot around the bush instead. so that the bush doesn't pivot & rub against the frame working a groove into the metal. do you see what I'm getting at ?
So in my opinion it seems as thought the bushing is frozen up inside the outer . does that sound right? have you encountered that before ? sure have not found anyone talk about it.
Or could it be the rubber has hardened to the point it won't allow enough pivoting for the suspension? As I noted before I've seen listings for new bushings but no mention anywhere about the rubber, other than that it gets destroyed upon removal of the bushings.
Thanks lots for your help & Advise

Posted By: Allan Gill

Re: Swing Arm Bushing Help - 05/17/19 9:15 pm

Don’t wish to appear rude but I think your over thinking this. The silent block bush is probably the wrong name as it isn’t a bush as all in the conventional sense, so named bush because it seperates the inner and outer at a fixed distance. To get any real movement takes half the weight of the bike plus rider weight, you really would struggle to move it by hand and the more it moves the more restriction it applies on itself. From 69 they changed the swing arm to a proper bronze bush system. So you then get smoother movement, lasts longer and a more possible feel with less chance of lateral play.

If the nut is tight enough though the bushes won’t move. If it’s any consolation it’s quite possible that the bushes in mine are the originals, I’ve certainly never changed them and the bike was in pieces from the early 90’s
Posted By: Doug F

Re: Swing Arm Bushing Help - 05/17/19 9:27 pm

Ok 1 more question then.
After doing more reading , about the bushings. & I admit I feel a little ignorant for asking. But the Rubber part is actually part of the Bushing itself then? seriously I was thinking in terms that the rubber was inside the swing arm & the Bushings were pressed into it. My bad just not getting my head wrapped around it correctly & not noting the book tells you they are inner & outer bonded together with rubber.
Just thinking about it all wrong , makes perfect sense now. Looks like I'll be needing to renew the bushings. I believe the rubber must be hardened to the point it's lost elasticity
Thanks again for help
Posted By: Mark Z

Re: Swing Arm Bushing Help - 05/18/19 5:13 am

The rubber is sandwiched between an inner and an outer metal sleeve. The inner sleeve fits snugly on the swingarm pivot and the outer sleeve fits snugly in the swingarm. As the swingarm pivots, the rubber twists. With time and corrosion, the inner sleeve becomes bonded to the swingarm pivot and can make it quite difficult to remove. If you have removed the swingarm pivot already, you're one step ahead. Getting the bushings out of the swingarm is the next hurdle. The inside of the swingarm is shouldered, so you can't get a drift on the bushing from the other side. Often the bushings need to be slit and peeled out. It's relatively easy to get the new bushings into the swingarm.

The only "silver lining" is that you'll probably never have to do it again.

Posted By: Doug F

Re: Swing Arm Bushing Help - 05/18/19 3:30 pm

Thanks Mark
Read a few tips about getting those things out. if I do go that route I'll try drilling out in between the bushings to get the inner freed from the rubber & try first pressing t out with the drill press.
I may go ahead & try using it the way iyt is & the pull it & check it for wear at the ends. It sure seems to me that the inner should not be pivoting with the swing arm & rubbing into the frame
but everyone says these things last forever so maybe I'm not seeing it right .
Posted By: Allan Gill

Re: Swing Arm Bushing Help - 05/18/19 7:59 pm

I'd be very surprised if the swing arm is actually rubbing the frame, it's very close but shouldn't rub the frame, the inner tube is a tight fit to the frame however. Unless your getting side play the rubbers are enterally fine.

If your not convinced, change them. The only thing I would say is get them from a reputable supplier, there is some junk out there and the two inner tubes don't line up when fitted.

The inner tubes tubes touch in the middle, the outer tubes don't... If that helps
Posted By: Tridentman

Re: Swing Arm Bushing Help - 05/18/19 10:28 pm

Unless the rubber has perished from age and/or oil mist then I would leave them be.
Getting them out of the swinging arm is a real pig of a job.
The couple that I have done over the years I needed at the end to burn the rubbers out and then remove the outer sleeve from the swinging arm.
On one occasion the smoke was such that some idiot neighbor called the fire brigade!
IMHO--only do this job if you really have to!
HTH
Posted By: BSA_WM20

Re: Swing Arm Bushing Help - 05/19/19 7:58 am

And unless you have owned the bike from new sp there fore know it's history, the swing arm rubbing on a frame is generally because the swing arm is bent from geting T-boned by a car or stepping out sideways into a pole.
They really are quite rugged .
The bloke who T-boned me wrote off his car while I managed to finish the days work with the bike running a bit crab.
Posted By: Allan Gill

Re: Swing Arm Bushing Help - 05/19/19 8:24 am

They might be heavy but they were built to last....
Posted By: Pelle

Re: Swing Arm Bushing Help - 05/19/19 7:39 pm

Originally Posted by Allan Gill
you should really preload the suspension before tightening the nut. ie, have the bike complete, have someone sit on the bike with the front brake on whilst you tighten it.


Good advice Allan, I'll keep that in mind when the "new" swingarm goes on my bike in a month or so. Didn't think of that the last time, but it makes sense considering the way silent blocs are supposed to work.
Posted By: Jon W. Whitley

Re: Swing Arm Bushing Help - 05/19/19 9:06 pm

I might just be missing it but what year A65 are we talking about here ?
Posted By: Doug F

Re: Swing Arm Bushing Help - 06/10/19 12:18 am

Thanks for all the info . sorry been a while since last post. been busy.
I'm going to give the old one a go. We'll see how well it does probably fine
Like you said earlier I,m most like over thinking the whole thing.

Hope to be riding soon !!
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