Is there any fix for this? Swing arm mount issue

Jramos13

Been Around the Block
Ok so i was removing a stuck swing arm that the bolt just rusted in, in the process i took away some material from the inner surface of the swing arm mount, i thought naybe some jb weld to fill in the space that is cut out, i dunno im open to any suggestion, here some pics:
 

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File it down flat and add a shim / washer to bring it back up to tolerance. We're only talking about a couple of mm - not enough to make it unsafe or anything.
 
Yeah don't over think this. Smooth it out a bit, reinstall and check side to side play. Chances are there won't be any.

Don't jam much in there - you don't want any binding. Keep it greased too. Is there a zerk on the swingarm to fill it with grease?
 
Make sure your engine is in and mounted before you test out whether you don't need any shimming......or you may find your engine mounts wont line up because you've squeezed the rear end of your frame together.


Also, if your swingarm pivot has dust caps, you can put a shim under them so you wont see it when it's all bolted back up.
 
Thanks for the replies!! Yes the bolt does have grease fitting at both ends, its for a TX500,

I dint thought at all about the engine mointa missaligning if the swing arm binds, appreciate that!

I will do that just file the rough edges and mount it to see if theres any play

Thanks!
 
It is important to understand how this assembly works. The swing arm bolt, along with the two steel bushings and center spacer, become a structural frame component when installed. Those parts get clamped fair down between the two sides of the frame, and the swingarm and its soft bushings (the factory ones are plastic) spin on this fixed assembly. Radial play is controlled by the bore of the soft bushings, and axial play is controlled by shimming between the frame and swingarm. Actually, on a TX500, the shims are located between the dust covers and the ends of the soft bushings. Likely you have not removed enough material from the frame to be of concern, but you want to file the area flat and perpendicular to the axle. If the face is angled, there will be excess pressure on one spot and axial play will wear prematurely. The missing material on the frame has no effect on the axial play itself, but if the face is not perpendicular, it will wear only in one spot instead of the entire face. You would have to remove a pretty good bit of material from the frame before it becomes a problem requiring a spacer to fill the gap. The axial play is determined by the difference in span of the stack of the two steel bushings and center spacer, and the stack of the two soft bushings and swingarm. When you assemble everything, you will simply tighten the bolt until the frame sides get pulled in tight to the center spacer/steel bushing stack. This will pull the frame sides together slightly more than before but very likely it will make no difference. Most Yamaha engines of that period are mounted to a horizontal cross member, so the engine installation will not interact with the swing arm installation.

File the area flat and perpendicular, and trial fit the dust covers, shims, steel bushings and center spacer into the frame without the swingarm. Without tightening the pivot bolt, look and see how much axial (side to side) play there is between the two sides of the frame. This is how much you will be moving the frame when you tighten it down. If you can tighten it down tight reasonable easily (tight is clamping the parts very tightly between the frame sides, not how hard it is to turn the nut) you should be fine. If it is a big gap, get a ground spacer/shim from a bearing house, or find a really close washer. It's ok to be bending the frame sides in slightly when you tighten the bolt. Just remember, the bolt is intended to be completely tight. It is not any sort of adjustment for the swing arm axial play.

Once you get that sorted out, assemble it again with the swingarm included. It needs to be operating room clean and lubed with some very light oil. Properly assembled and shimmed, there should be ZERO discernible play either radially or axially. If there is axial play, add shims. You can get them from a bearing supply. Likely there are some already inside the dust caps. They are razor thin and usually overlooked by a lot of people - usually glued in with old grease pretty good and easily mistaken for part of the cap. If there are none and you need some, get them from a bearing supply. They should fit pretty closely inside the cap, but have an inside diameter larger than the OD of the steel inner bushings. When you get zero play, take it apart and re assemble everything with wheel bearing grease. It should be quite tight - enough that the arm barely falls from its own weight when held horizontal. Don't worry - it will get a lot freer once you start riding.
 
Wow, that was very in dept and really helpfull, appreciate that!

This question might sound stupid but forgive me as english is not my first language, when you say file perpendicular, do you mean to just file the surface till everything is flat and in the same level? Also filing down the part that is not cutted out from the inner surface of the mount?

Thanks!
 
Yes, I would file down even the part that has not been cut accidentally. By perpendicular I mean perpendicular to the swing arm bolt or 90 degrees to it. In other words, file a new surface exactly like the original surface keeping it nice and square to the frame like the original. That will result in an original condition with the span between the frame sides very slightly wider than before. Squeezing them in when you tighten up the bolt will of course twist the frame sides very slightly, but if you think it excessive, you can add the washer to make up for the missing material. This would probably be a pretty thick washer being big enough diameter to be a spacer, I would file it down in order to be thin enough to be a proper fit. The important thing is that there is no value in welding the metal back on and re-machining it. I'll also admit to being more concerned than most guys over this particular part of a motorcycle. I think it is often much overlooked and more critical to performance than most people realize. Many old bike drive and handle remarkably well once you get all the slop out of the suspension. Most guys are so used to riding them with bad swinger pivots, original ball bearing steering heads, and poor damping they just assume the handling is what it is, when in fact making a huge improvement is quite cheap and easy. The swing arm pivot is especially important as the tiniest amount of slop is so greatly magnified way out there where the tire touches the road. Most all modern bikes use much higher precision roller bearings that bolt up with practically zero tolerance so evidently the factories think so too!
 
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