Swing arm design

gggGary · Full Member Joined: Jan 07, 2009 Posts: 114

1983 Heritage special 10K miles good condition. I had some side movement at the axle so I bought a set of bronze bushings from Mike's and took er apart this morning. cleaned everything up and started to see what i had. I think I am confused. the parts I have are the frame the Pivot bolt, the machined sleeve the two bushings the two grease seals and the swing arm. after removing the grease with solvent. It had all been kept well greased. I became confused. It is obvious that the machined sleeve turns on the pivot bolt. (wear, polish marks) Isn't the machined sleeve supposed to turn in the bushings? I can see no mechanism that allows the take up nut on the pivot shaft to apply pressure to the machined sleeve to lock the two together so that the pivot motion is between the sleeve and the bushings and not between the sleeve and the bolt. I think there is too much space to crush the frame together enough to hold the sleeve in place on the shaft. without those two being locked together then the bushings aren't really bushings? Anyone else noticed this or am I missing something? I am thinking a shim between the grease seal and the frame to get the tolerance out of the set up so that I can draw the frame parts together enough with the nut to lock the sleeve to the shaft would be the best thing to do. I would like to hear some opinions on this. gggGary, Riding season is here at least on the better days. I have to admit I have 7 XS650's now so I can run one of the other ones but I want this one back together also.

yamaman · Posted: March 19, 2009, 12:51 pm Post subject: Re: Swing arm design

Is it just me, or is that post impossible to read? A few paragraph breaks would be great!

Plenty of posts here on swing arm rebuilds, use the google search button. Amazing how much these frames spread when you pull the s/arm out.

Cheers

Retiredgentleman · Posted: March 19, 2009, 1:20 pm Post subject: Re: Swing arm design

I agree yamaman. Posters will get more answers to their questions, if they use paragragh breaks, and punctuation.

If I find it difficult to read, I just stop reading and move on to another post.

gggGary · Full Member Joined: Jan 07, 2009 Posts: 114

OK here is a cleaned up version!
I am working on a 1983 Heritage special with 10K miles good condition. I had some side movement at the axle so I bought a set of bronze bushings from Mike's and took er apart this morning.

I cleaned everything up to see what i had. Every thing is there I am sure this is the first time it has been apart. It had all been kept well greased.

The machined sleeve has been turning on the pivot bolt. (wear, polish marks) Isn't the machined sleeve supposed to turn in the bushings not the pivot bolt?
I can see no mechanism that allows the take up nut on the pivot shaft to apply pressure to the machined sleeve to lock the two together, so that the pivot motion is between the sleeve and the bushings and not between the sleeve and the bolt. On other bikes I have worked on there is a threaded collar that draws everything to one side of the frame and then is jam nutted to lock it all together.

I think there is too much space to crush the frame together enough to hold the sleeve in place on the shaft. without those two being locked together then the bushings aren't really bushings? Anyone else noticed this or am I missing something? I am thinking of trying a shim between the grease seal and the frame to get the tolerance out of the set up. Then I can draw the frame parts together with the nut to lock the sleeve to the shaft.

I would like to hear some opinions on this. It also appears the the flanges on Mikes Bronze bushings are a bit thinner than the phonolic bushings which will make the situation worse.
gggGary

yamaman · Posted: March 19, 2009, 1:33 pm Post subject: Re: Swing arm design

Thanks mate, I'm sure you'll agree, that is much easier to read.

As I said earlier, the frame springs apart a long way when undone. Lots of people with those bushes & I havn't heard any problems.

Just put it back together & I'm sure you will find it's ok.

Cheers

jayel · Posted: March 19, 2009, 3:09 pm Post subject: Re: Swing arm design

need mikes up dated swingarm bolt too, 16mm full lenght the old ones necked down at the thread

gggGary · Full Member Joined: Jan 07, 2009 Posts: 114

Well just out of the nick of time I got a fleabay Yamaha owners manual in the mail today.
The manual refers to thrust washers inside the grease seals. That was an aha moment. I haven't seen reference to those on here or elsewhere. I will look for any thrust washers in there now and if not I will put a dial indicator on the play and add some.
Has a swing arm pivot bolt ever broken at the thread? I would think if thrust washers take up the play it should not take great torque on the nut to "snug" things up properly. The manual refers to thinner thrust washers if there is binding but does not mention what thicknesses are (were) available. I am still not sure if Yamaha meant the steel bushing to float on the pivot or if it should be captured by tension from the pivot nut.

bluebikerblan · Posted: March 19, 2009, 4:12 pm Post subject: Re: Swing arm design

The pivot bolt has often been a failure point (just where it necks down to the thread on the stock bolt). I have now come across two....one broken and one badly stress cracked on old bikes I've rehabbed. In both cases, this allowed the frame to spread and constitute a signifigant danger....way more than just a wobble. The beefed up pivot bolt from Mikes is a very, make that a VERY good idea. This failure point has long been noted through the years. I am aware of same in Yamaha 650 Society publications and the upgrade has long been suggested in many
places

Opinion... The pivot rod is obviously in a fixed locked in postion relative to the frame. The bushings when pressed in the swingarm are also then fixed relative to the swing arm. The required rotation is therefore the bushing surface rotating around and against the pivot shaft. All the spacers are intended to do is eliminate loose play of the swing arm assembly along the pivot bolt and to retain grease. Best, Blue

ps to TRG .....Just checking on the shoes. I'd be glad to donate replacements too. Your perspective on GB is shared by many including me.

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

Hey, we got so many custom builders on here I been wondering: How come nobody makes a custom swingarm for the sixfifty? I'm thinking of a pair of rectangular steel bars trailing back from the shaft. The bars are drilled crosswise to save weight, and chrome-plated for looks.

How come nobody makes a swingarm like that and sells them here?

gggGary · Full Member Joined: Jan 07, 2009 Posts: 114

bluebikerblan wrote:

Opinion... The pivot rod is obviously in a fixed locked in postion relative to the frame. The bushings when pressed in the swingarm are also then fixed relative to the swing arm. The required rotation is therefore the bushing surface rotating around and against the pivot bolt. All the spacers are intended to do is eliminate loose play of the swing arm assembly along the pivot bolt and to retain grease. Best, Blue.

OK Good to know on the pivot bolt.
Couple more points. What you describe (and I agree) still leaves two potential rotations, pivot bolt to steel bushing and steel bushing to (now) bronze bushing. Is that intended?
Second point Yamaha has a part number for bushings intended to go inside the grease seal to take up the side to side slack. Perhaps overtightening the nut on the pivot bolt to draw the frame together and remove slack is what has caused failures at the pivot bolt shoulder? The manual procedure is to install bushing(s) to take up the slack. Then excessive tension on the nut is not needed?

Does anyone know the thickness of the called for Yamaha Shim 2402212700? inquiring minds....

bluebikerblan · Posted: March 19, 2009, 7:03 pm Post subject: Re: Swing arm design

Please note edited correction should read "around and against the pivot
shaft " not bolt...ie bolt through shaft which rotates against the greased bronze bushing surface. Blue

gggGary · Full Member Joined: Jan 07, 2009 Posts: 114

I measured 1.7mm of space between the frame bushing faces and the assembled steel bushing and grease seals. That is a huge amount to draw in the frame to my mind. A frame cross member is not far from this area that needs to be drawn together. So I think the drawing together of that amount has to do bad things to bushing alignment, pivot shaft flex etc.
I noted that the thread on this pivot shaft had a damaged area. I believe this bike has never been apart in this area before yesterday. My guess is that Yamaha just jammed that nut on with an impact wrench set on high crushing the frame together. It was obvious on my bike at least that the steel bushing has been turning on the pivot bolt. I agree that it shouldn't. I am planning on fitting one or two shims between the grease seal and frame bushing so that a moderate tightening of the pivot bolt nut should capture the steel bushing without excessive torque on the nut. That is my hope anyway. Thanks for your replys.

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