Yet Another Swingarm Bushing Thread

[gggGary]

My usual comment on this discussion; after end play is set; assemble into frame and check for excessive clearance between frame and assembled swing arm components, if needed add some 3/4" machine bushings to take up any gap, don't just reef the crap out of the pivot bolt to rack the frame, bend the frame bosses out of alignment, put bending forces on the pivot tube and bolt, perhaps causing the threads on the pivot bolt to fail. I've found some that needed extra bushings, some that were fine,

 

[YamadudeXS650C]

Yes, I think the .040" is the max wear limit. I've never seen a minimum spec listed in any of the manuals for the original plastic/nylon bushings. Maybe it's not a factor? Maybe the collar will compress some if need be when the pivot bolt is torqued, so the pivot tube protrudes out past it and can get pinched between the frame mounts. Maybe the minimum spec thing is more for the bronze bushings.

That tech bulletin doesn't really give a min and max, just one spec, .005". I don't like dealing with single number specs, lol. I prefer to be given a range.

My thinking in regards to this 12/73 Yamaha Tech Bulletin about the bronze bushing upgrade is that the .005" sideplay number is a target measure number for the pre-assembly distance from the bush collar to the end of the pivot tube, procured in the manner that I presented in my post #1 photos. I am currently comfortable with the .008 I settled on, and the assembly went well tonight in accordance with the torquing procedure that you presented in post #16.

Therefore, I would recommend, at least at this time, and pending further commentaries or evidence, a pre-assembly sideplay target measure of about .008.
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[joebgd]

[QUOTE="fredintoon, post:
My proposed switch from stock to a solid bar tapped M16 each end and retained by M16 capscrews each side
that are reefed up REAL tight will work far better.[/QUOTE]
Do you have any pics of this? I'm not sure I can picture it.

 

[David Toll]

I shimmed mine out to .02". Used one of the original shims that was on the bike, (circa '78), and one I got from Heiden Tuning. These shims were different thicknesses so I took the clearance measurement by putting the pivot shaft flush with one end of the tube, mounting both shims on the other and measuring the distance between the shim face and a straight edge across the pivot tube, just like Yamadude shows above. I then put the shims on either end. I assume that the different thicknesses of the shims will not cause me grief, (i.e. "death" wobbles, tighter cornering on the thin shim side, that kind of thing?? Only kidding!).
I remember inquiring about this stuff earlier this year and the general response seemed to be that I needed a "few thou" of the pivot tube exposed so that the frame could grab it. Good to see some specific figures being touted even if the range between .005" and .040" seems quite large. Looks like my .02 sits around the middle.

 

[YamadudeXS650C]

even if the range between .005" and .040" seems quite large

Hey David,

As you read in my posts last night, it now seems evident that the .040" figure is a wear limit for inspection purposes to be applied later, after many miles of use, and therefore not a figure which we would want to be using when we are doing our pre-assembly bench set up in the manner which you have just described, and I pictured in post #1.

...which leads me back to the notation I had made in my personal hand written notes a few years ago, which was [ .006" - .020 ].
This span of pre-assembly freeplay or sideplay, set at the bench, using shims or no shims depending on one's own particular assembly, is a figure that I seemed to have extrapolated from the data at hand (including some of the gaps or "vagaries" in the literature, as 5T mentions), and including the experience that I had with my '76 XS swingarm at that time. Today, however, I am inclined to suggest a target figure of .008 and a range of .006" to .010" *, followed by assembly and the torquing process suggested by 5T above in his post #16.

* add the appropriate thickness shim if your sideplay is greater than this.

....pending further offerings of commentary and/or evidence.

 

[Mailman]

I like it Dude! You’ve obviously done your homework ( and mine for me ) Thanks!
Now I just hope my job goes as smoothly as yours when I get ready to do it.
Might be a while , it’s riding season here in Phoenix!

 

[Mailman]

I think this would make an excellent addition to the tech section!

 

[David Toll]

Yes Dude, I have 1 more of the Heiden shims so I will follow your well considered advice and narrow the gap and then 5T's assembly and torque suggestions. Steered correct yet again by the Forum! Thanks gents.

 

[YamadudeXS650C]

Today I dismantled the swingarm of my '76, in which I installed bronze bushings a number of years ago, to re-check the sideplay and inspect the components.

I captured a better photo of the pre-assembly sideplay measurement process which uses a feeler gauge.

 

[YamadudeXS650C]

The results of my torquing procedures, per the recommendation of 5T:

> The '80 was set at .008, and the arm fell slowly at about 38 ft. lbs.
> The '76 was set at .010, and the arm fell slowly at about 42 ft. lbs,
the results of which seem to validate that the .006 to .010 range of pre-assembly sideplay is a good starting point.

Note: I compiled the essentials of this thread into a new one for easy reading:

http://www.xs650.com/threads/installing-bronze-swingarm-bushings-and-setting-sideplay.51077/
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