Custom Swingarm Bushings (for swinger conversions)

[T8erbug]

I have a GS750 and am converting it to accept the GS1100 allow swingarm. As many of you know who have been around here for a while or who have already done the swap the choice in conversion basically boils down to boring out your frame to accept the larger diameter GS1100 pivot OR machining your own bushings to make your 750 pivot work with the 1100 swinger. I have opted for the bushing route because I just don't want to take the risk of drilling into the frame and having holes that are not concentric. NOW to my question for all of you GSers. What material should I use for my bushings? What are the stock bushings made out of? Where can I get round stock for a decent deal? Lastly when I get this done there is a good chance I will have spare bushing material machined to the correct dimensions for a GS750-GS1100 swinger swap so if anyone wants to buy the rest of it I'll give it to them at my cost for parts (free labor). PM me. Answers one or all of these questions would be most appreciated! Thanks guys

 

[GregT]

The fitting is a tad more difficult than you imagine as the bushings are actually roller bearing inner races hence hardened....
You can of course make them up from a suitable steel and have them hardened and finish ground...but...$$$

Bore the frame.

 

[Guest]

The fitting is a tad more difficult than you imagine as the bushings are actually roller bearing inner races hence hardened....
You can of course make them up from a suitable steel and have them hardened and finish ground...but...$$$

Bore the frame.

Like he said bore the frame, you are not going to be off enough to notice unless you drill totally off center of your existing hole, which I don't know is really possible

 

[T8erbug]

Yeah I want to steer away from having to drill into the frame for as long as I can. That will be my last resort. If there's one thing I have learned while alter bike suspension it's that the smallest amounts of adjustment can have a huge effect on handling. I just don't want to end up with a bike that doesn't track straight because my bored out holes are off by a 1/2 a mm. Unless someone knows of a way to bore the holes out while keeping them concentric. . Drilling just seems a bit like the "get a bigger hammer" kinda method. I'm up for ideas though

 

[Agemax]

take the frame to a machine shop, they should be able to make up a jig in order to drill the holes accurately

 

[Guest]

Like he said bore the frame, you are not going to be off enough to notice unless you drill totally off center of your existing hole, which I don't know is really possible

It's possible, believe me, that is what happened to me.

 

[salty_monk]

I think you'd need a jig to be 100% sure....

I think Katman might already make the reducers. Should be pretty easy to make

 

[Greg B]

If there is enough difference between the pivot bolt diameter
& the ID of the inner bearing race you could get away with just
a sleeve.
Preferably at least 1.5mm wall thickness. 2mm would be better,
And I don't think I'd chance it at 1mm.
I'd choose 4140 for the sleeve material, but truthfully, regular
old C1018 would be fine. Bond the sleeve to the inside of the
inner race with Loctite RC680, and it'll never come out.
Well until you heat it to around 600 degrees anyway.
Again this is assuming you have adequate wall thickness to your sleeve.
If not I would not try this.

 

[Smurf]

T8erbug,

Which way did you decide to go?

 

[T8erbug]

T8erbug,

Which way did you decide to go?

I thought a lot about the bushings but going from 14mm to 16mm would only require a spacer with 1mm wall thickness which is pretty small and I'd imagine suseptible to warpage/damage plus allows for a lot more play in chassis parts. The less parts the less I have to rely on perfect tolerances to keep the play out of the swingarm and suspension components. Therefore I decided to go the drill-out route. I am in the middle of it right now and I will hopefully document it thouroughly enough so that people doing the same thing can do a better job if they decide to go the same route. I'm going to use a step bit on the inside and outside of each pivot arm mount in the frame, drill through, then ream to just under 16mm. I think this will give me concentric holes and if not it will be dang close. Then I will just emery cloth the pivot bolt until it fits snugly in the newly reamed holes. It shouldn't take much but time and care to make good holes. Wish me luck. Check out my build thread (T8erbug's GS750 Cafe Racer)

 

[Smurf]

Any news, T8?

 

[T8erbug]

Any news, T8?

I have looked and looked for the right tools for the job and finally found someone with them but he went to Canada for the weekend. Mutha.. So as I sat here and contemplated what I was about to do I thought I'd give ONE more thing a try. Since I started this post I have actually come in contact with a very very valuable resource. His name is Ben and he works at a GIANT machine shop near me and he has been helping me a ton with custom parts for my bike. They have quite a few lathes there and I talked to him last night about making a new inner bearing bushing out of steel then hardening it. He said as long as the tolerances don't have to be super tight (super tight to him at that machine shop is like .00001 haha) we can handle it. Therefore I have REchanged my mind and will be waiting for Ben to get back from Idaho till Jan 5. Smurf, if our experimental part works I'd be more than happy to make one for you as well and I'll just charge you cost plus a little bit for Ben to do the lathe work (nothing compared to normal machine shop rates)

 

[Smurf]

T8,

I'd definitely like a pair of the custom inner races. I checked with a machine shop here in Allentown and they refused to even try, saying it would be $800 if they even agreed to do it. So the custom inner races would be 25x14x30 to sleeve the stock 1100 bearings (25x33x30) down to 14x25x30?

If that doesn't work out, I talked to a guy and Bearings and Drives Unlimited. He said he could come up with a series of 3 inner races that would sleeve the 25mm stock 1100 bearing down to the 14mm 750 pivot bolt.

Each side would need:

1 JR20X25X30 ($17)
1 JR17X20X30,5 ($13)
2 JR14X17X17 ($12)

Note that the middle race would need .5mm cut or ground off and the innermost race would need to be shortened 4mm. Not sure how well that would go with hardened steel. So this method would cost $108 ($54 each side) plus the bearings ($40 at the dealer) and require pressing the bearings to be pressed together.

So I think I'll wait to hear if you can get the custom races made. Good Luck and please keep me posted!

 

[daturat100r]

Greg b 's solution of bushing sleeves is ideal and no need to be concerned about wall thickness as long as they are a good fit.Turn the bushes on a mandrel and turn up a shouldered punch to press them in so to prevent collapse of bush and once in drive a 14mm bearing ball thru the hole to broach it to size.If you can fit a 6 thou thick liner to a valve guide and it stays in place with no adhesive it will b no problem to sleeve the bushes down to size and b confident it will not fail

 

[Chuck78]

The fitting is a tad more difficult than you imagine as the bushings are actually roller bearing inner races hence hardened....
You can of course make them up from a suitable steel and have them hardened and finish ground...but...$$$

Bore the frame.

I've read this numerous times, and it is not quite true. See my photo in the recent "swingarm swap and cleanup" post- the bushing you will be machining does not have to replace the stock inner spacer & both bearing races. You just need a spacer just a hair under 225mm I think it was, that is 14mm i.d. and 16mm o.d.

The inner races are sandwiched between the frame, dustcaps, thrust washers, and inner bearing race spacer sleeve. You just need a spacer to make the 14mm bolt 16mm thick between the frame, and have it machined just a hair narrower than the frame as to allow the frame and pivot bolt to sandwich the inner race assembly properly to keep it fixed in the frame and avoid it rotating. I would use permanent loctite on the spacer to keep it from rattling around side to side. I put my calipers on the swingarm with the bearings, races, spacer, thrust washers, and dust caps installed, and if I remember correctly, it measured right around 225mm. My calipers don't go that wide, but I measured pretty carefully in two steps to come to that almost exact measurement. The 750 and 1100 pivot bolts measured DEAD ON to 14mm and 16mm on their shoulders. I would make a spacer around 224.6mm wide to allow for frame flex to tightly sandwich the inner races as an assembly between the frame. As one other member posted, use permanent loctite to keep the inner spacer from having a chance to move around or rattle.

My machinist buddy told me he could make one of these and two rotor spacers for the twinpot mod on his lunchbreak! I haven't gotten around to re-checking the width, but that measurement I would be pretty darn confident on as-is. I had asked him about steel, but I also had wondered even how aluminum would work, as it is just there to keep the assembly centered. maybe aluminum would be too soft for harsh road conditions? If he can easily make it from steel, then that's the ticket.

EDIT - sorry I posted that before reading the rest of the thread, so some of it is rehash.

 

[T8erbug]

Greg b 's solution of bushing sleeves is ideal and no need to be concerned about wall thickness as long as they are a good fit.Turn the bushes on a mandrel and turn up a shouldered punch to press them in so to prevent collapse of bush and once in drive a 14mm bearing ball thru the hole to broach it to size.If you can fit a 6 thou thick liner to a valve guide and it stays in place with no adhesive it will b no problem to sleeve the bushes down to size and b confident it will not fail

I've read this numerous times, and it is not quite true. See my photo in the recent "swingarm swap and cleanup" post- the bushing you will be machining does not have to replace the stock inner spacer & both bearing races. You just need a spacer just a hair under 225mm I think it was, that is 14mm i.d. and 16mm o.d.

The inner races are sandwiched between the frame, dustcaps, thrust washers, and inner bearing race spacer sleeve. You just need a spacer to make the 14mm bolt 16mm thock between the frame, and have it just a hair narrower than the frame as to allow tge frame to sandwich the inner race assembly properly. I would use permanent loctite on the spacer to keep it from rattling around side to side.[/QUOTE

I'll go check it out. Thanks for the feedback guys. So Chuck you're saying just go the sleeve route? It makes sense to do that as long as the tolerances are tight just because there is less to do workwise and I won't have to harden the steel, BUT the fact that it only has 1mm wall thickness leads me to believe it would be tough to make on the lathe. I'm not the experienced machinist ha I just come up with the crazy ideas! Daturat100r just about everything you said while probably being 100% correct it went right over my head ha. Any youtube vids you could link me up to so I can get a visual of what you're saying?

 

[Chuck78]

So Chuck you're saying just go the sleeve route? BUT the fact that it only has 1mm wall thickness leads me to believe it would be tough to make on the lathe.

Good point, I will check with my machinist friend, but he already told me that a 224.6mm wide 16mm o.d. 14mm i.d. steel sleeve would be really simple to make,.

I had thought about jigging up a small drillpress in the frame and buying a 16mm reamer bit to enlarge the holes, but I didn't want to permanently alter the frame so that the 750 swinger would never fit again in case I ever upgrade to a different (80's GS1000/1100) frame or stripped parts off to build a better GS superbike. Also the repercussions of failing to drill it straight were weighing heavily. The amount of time to set up a jig to hold a small drill press perfectly perpendicular to the frame holes/bushings seemed not worth it if my buddy can just make a spacer on his lunch break as he said.

 

[Chuck78]

I just had a crazy thought that if drilling/reaming out the frame, getting a 16mmx1.0 thread tap off of ebay through the frame would probably make drilling/reaming the 16mm hole a lot easier, as the thread tap would probably be more likely to guide itself really straight through the hole, and ream out half of the metal at the same time. Then running a 16mm reamer through would be pretty easy.

I don't know if this is the best type of reamer to use, but here's the best of the 16mm I could find on ebay:
http://www.ebay.com/itm/180985951610

a 5/8" reamer I linked in that other post I mentioned seemed to be the style that I think would work the best. I am still in favor of having a 1mm thick 225mm wide spacer sleeve made.

 

[Chuck78]

http://www.thegsresources.com/_forum/showthread.php?t=190634

 

[T8erbug]

Good point, I will check with my machinist friend, but he already told me that a 224.6mm wide 16mm o.d. 14mm i.d. steel sleeve would be really simple to make,.

I had thought about jigging up a small drillpress in the frame and buying a 16mm reamer bit to enlarge the holes, but I didn't want to permanently alter the frame so that the 750 swinger would never fit again in case I ever upgrade to a different (80's GS1000/1100) frame or stripped parts off to build a better GS superbike. Also the repercussions of failing to drill it straight were weighing heavily. The amount of time to set up a jig to hold a small drill press perfectly perpendicular to the frame holes/bushings seemed not worth it if my buddy can just make a spacer on his lunch break as he said.

It seems we sit in almost the same spot haha. My buddy can do the machine work too and it's just a matter of the bushing/sleeve actually working. My hesitance to drill goes through stages . . Somedays I'm about ready to go out in the garage with my mikita and a drill bit and just go to town. I have waited long enough though I might as well do it right. I'm a little ocd so knowing that my bike could have vital holes that are off center would ruin the whole bike for me because it's not symmetrical.. . My buddy won't be back in town till the 5 of Jan so I'm stuck waiting. When will you be able to get your sleeves done?