Re: First Vintage Race Inspired Smoker
The fiche is all correct except that - like all Yamaha parts exploded views of this era that I have seen - the shims are completely absent. There is no part number(s) I am aware of and I have never been able to get more info from Yamaha. Part # 7 is not a shim, but a washer that goes outboard of the frame under the nut(s) that clamp up the assembly. I can understand that confusion would likely arise when the part is not listed, but trust me, nearly all bikes have them whether shown on the exploded parts view or not. Very nearly every bike I have taken apart - and this is a substantial number - have factory shims in the swing arm assembly, though I have seen a few with none. I am certain that those bikes were deemed to not need any shims due to the chance size of the parts involved and I am sure the factory assembly allowed for more slop than would be deemed optimal! They are VERY easy to miss, as they fit inside the end caps and with old grease all dried up can be easily overlooked. That is irrelevant as the shims you need after replacing any of the parts will almost certainly be different than what it needed with the previous parts. The shims are to take up the tolerance in manufacturing the other parts. The outside diameter of the shims is about the same as the outside diameter of the outer (bronze or nylon) bushing flange, maybe just a bit smaller. The inside diameter is a bit larger than the outside diameter of the steel inner bushings. The stack of the two steel bushings and the center spacer should be very slightly longer than the out to out of the bronze bushings pressed into the swing arm. Assembled with out shims, the arm will slide this difference side to side. The shims are there to reduce this play to zero. There are many sizes (thickness) of shims, though most of them are razor thin like aluminum foil thickness. All of the shims that I have have come from parted out bikes, so I can not offer a practical supplier, but shims are shims, and a bearing jobber will be able to get you what you need if the E-Bay purchase does not work out. For the record, I have had a couple of instances where the span of the inside to inside of the frame was wide enough to need some "shims" to fill the gap. These would not be called shims - technically they would be (were) spacers. Similarly I have had frames that were a bit too narrow and wedging the whole works in was pretty frustrating to not damage the new paint. Both conditions are irrelevant to understanding getting the fitment of the arm right. In the case of a too tight frame, the stack of end caps, inside bushings and center spacer simply has to wedge the frame sides apart a tiny bit, but that has no effect on how much space is between the end caps and the outer bushings and swing arm. The same assembly on a too wide frame will need exactly the same shims. If you don't add an extra spacer to fill the gap, tightening the swingarm bolt will simply tweak the frame sides together to eliminate the gap. For me, if the gap is big enough I add a thin spacer so as not to bend the frame sides in so much, though I doubt it really harms anything.
Edit: The shims go in between the outer bushing and end cap (parts #4 and #6). The inside bushing (Part #5) is clamped tight against the end cap and is centered inside the shim(s) but does not touch the shim(s). They are rings nearly the same inside and outside diameter as the flange of the outer bushings. When correctly assembled, the two end caps, the two inner steel bushings and the center spacer are clamped tightly inside the frame. All these parts along with the swing arm bolt, the two nuts and washer (and the grease fittings) clamp tight with the frame and do not move. The swing arm, the two outer bushings, and whatever shims are needed, fit between the two end caps, and are free to rotate with the arm.
There is of course an alternative to adding shims. That would be to put it together and measure the side to side slop. Then you would take it back apart and shorten one of the steel inner bushings (or center spacer) this amount less maybe half a thousandth of an inch which would be the new slop which is nearly nothing which is what you want. This has the drawback of 1) being permanent, 2) if you overshoot, you then would have to remove material from one of the outer bushing flanges to gain back the tolerance, and 3) making the whole works slightly narrower causing you to have to draw the frame sides in that much more (or add a spacer to compensate!). So plan on shims. Put your rear suspension together and check the play. Add shims until tight. Remove shims until free but zero play. Reassemble with grease. The result will be perfect in five miles.
