reepicheep
Member
- Apr 3, 2009
- 670
- 2
I'm rebuilding a pretty beat up KDX-220 for a friend, and tearing the back end down last night to deal with some pretty bad swingarm play, I figured out that the previous owner had gone with nylon bushings instead of bearings. I figured I would post the results from what we saw (I can get some pictures if anyone cares)...
The bushings were an interesting and straightforward looking install. Basically, it looks like they found the right size rod (I am assuming some sort of high density polyethylene or something).
Then they apparently just cut it to length, drilled the right sized hole down the center of it, and pressed it into the place where the bearings went.
So in this case, the nylon bushing replaced the needle bearing cage, the needle bearings, and the inner spacer that goes over the bolt that the needle bearings typically ride on. The bolt was the bearing surface riding on the nylon.
Now if you had asked me before, I would have said this is a bad idea and it is doomed. You have lost the steel spacers that take the compression load of the bolts. Seems to me that when you torque those bolts (the swingarm bolt in particular at 88 newton meters) you would deform the plastic bushing and things woudl bind up... for a while until they wear down, then you would loose the right torque setting on that bolt and other bad things would start happening.
In practice though, before we tore this bike down, aside from the play in the lower shock mount bushing (more on that in a second), it seemed fine. The swingarm moved OK, there wasn't obvious lateral play in it, and the bolt when removed was still on nice and tight.
As for the bushings themselves, the swingarm ones looked pretty solid. They were slightly oval shaped, but not bad. Nowhere near failing. The bottom shock mount bushing (which is the bearing that is always the worst anyway) was *badly* ovaled... perhaps half the width of the bolt again. So if you lifted up the rear end or put it on a stand, you could hear that shock clunking around back there. I wish I knew how many hours were on there, I'll try and find out.
But, aside from the clunk (which might annoy you if you let it), the whole setup was still working pretty good, and was still a long way from failure.
All in all, the bearings are probably the better solution for most of the S-Brace. If you service them once a season or so, or put in a zerk fitting, I suspect they will last just about forever. But for that lower shock bearing, that poor undersized little guy that drags through ever puddle, maybe the plastic bushing isn't such an awful idea. Particularly if you can get a 3' long rod of that heavy plastic for $10, and just slice off 15mm or so once a season and slap it in the drill press to bore a hole in it. Put in a new piece every season, and $10 could last you 10 years, and you would always have the parts you need in the garage without running out to the store.
I'll also go up to the local bearing wholesaler when I get the chance and see how much the non factory version of that bearing costs. It's probably less then $5 wholesale anyway, so its probably not a big deal either way.
The only other issue from the whole setup that we ran into was that the bushing width on the swingarm was narrower (they eliminated the metal spacer in the center, and the metal spacers and seals on either side). As a result, when he bolted down the motor it was a little to one side, making it impossible to get the swingarm with the factory spacers and seals in there. So we had to loosen the bottom motor mount bolts (just loosen, not remove), then fit in the swingarm, then bolt the motor back in.
(Come to think of it, I think I had to do that on my rebuild as well, and that was gooing from stock to stock, so that may not even be an issue related to the bushings...)
So anyway, FWIW, there is a data point... I'll try and find out how many seasons were on that bushing. If I can, I'll post pictures of the wear.
The bushings were an interesting and straightforward looking install. Basically, it looks like they found the right size rod (I am assuming some sort of high density polyethylene or something).
Then they apparently just cut it to length, drilled the right sized hole down the center of it, and pressed it into the place where the bearings went.
So in this case, the nylon bushing replaced the needle bearing cage, the needle bearings, and the inner spacer that goes over the bolt that the needle bearings typically ride on. The bolt was the bearing surface riding on the nylon.
Now if you had asked me before, I would have said this is a bad idea and it is doomed. You have lost the steel spacers that take the compression load of the bolts. Seems to me that when you torque those bolts (the swingarm bolt in particular at 88 newton meters) you would deform the plastic bushing and things woudl bind up... for a while until they wear down, then you would loose the right torque setting on that bolt and other bad things would start happening.
In practice though, before we tore this bike down, aside from the play in the lower shock mount bushing (more on that in a second), it seemed fine. The swingarm moved OK, there wasn't obvious lateral play in it, and the bolt when removed was still on nice and tight.
As for the bushings themselves, the swingarm ones looked pretty solid. They were slightly oval shaped, but not bad. Nowhere near failing. The bottom shock mount bushing (which is the bearing that is always the worst anyway) was *badly* ovaled... perhaps half the width of the bolt again. So if you lifted up the rear end or put it on a stand, you could hear that shock clunking around back there. I wish I knew how many hours were on there, I'll try and find out.
But, aside from the clunk (which might annoy you if you let it), the whole setup was still working pretty good, and was still a long way from failure.
All in all, the bearings are probably the better solution for most of the S-Brace. If you service them once a season or so, or put in a zerk fitting, I suspect they will last just about forever. But for that lower shock bearing, that poor undersized little guy that drags through ever puddle, maybe the plastic bushing isn't such an awful idea. Particularly if you can get a 3' long rod of that heavy plastic for $10, and just slice off 15mm or so once a season and slap it in the drill press to bore a hole in it. Put in a new piece every season, and $10 could last you 10 years, and you would always have the parts you need in the garage without running out to the store.
I'll also go up to the local bearing wholesaler when I get the chance and see how much the non factory version of that bearing costs. It's probably less then $5 wholesale anyway, so its probably not a big deal either way.
The only other issue from the whole setup that we ran into was that the bushing width on the swingarm was narrower (they eliminated the metal spacer in the center, and the metal spacers and seals on either side). As a result, when he bolted down the motor it was a little to one side, making it impossible to get the swingarm with the factory spacers and seals in there. So we had to loosen the bottom motor mount bolts (just loosen, not remove), then fit in the swingarm, then bolt the motor back in.
(Come to think of it, I think I had to do that on my rebuild as well, and that was gooing from stock to stock, so that may not even be an issue related to the bushings...)
So anyway, FWIW, there is a data point... I'll try and find out how many seasons were on that bushing. If I can, I'll post pictures of the wear.
