Need info: katana swingarm on a gs450

Shaun6691

New Member
Hey guys. I've got an 82 gs450 cafe and want to adapt a 1st Gen katana (83) swing arm to her. Has anyone ever done it? Or can atleast offer some info? It's the same swingarm on the gs1100e's. I'm also on the gs resources forum but I've come up empty over there as well. Any info is appreciated. Oh and here's my bike. I call her the smurf.

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You will probably need to widen the mounting location to accept the new swing, or fab up new mounts.

Brace the shit out of the frame to handle the changed stress tensors.

Offset front sprocket to line up with the rear.

Did i mention to brace the shit out of the frame?
 
I don't want to half ass anything so I'll reinforce it. I don't even have the swing arm yet. Picking up this weekend. Just trying to develop a plan right now.

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The frame will be fine.


Width at the pivot will be the problem.


GS450 swingarm pivot is 200MM - not sure what the 1100 is but pretty sure it's a fair bit wider.


GS500 arm is 205mm I think - you could trim that down and weld on some shock mounts.
 
I've actually considered that too. I just LOVE the look of the katana arm. I've looked everywhere and I can't find the pivot width listed for the katana arm vs. the rather half thought out looking gs500 arm. I saw a build thread about a guy putting on a katana arm on his 78 gs400 and it was a matter of reaming out the pivot tube through the frame and using differ bearings. Now that I think about it, that sounds like a lot of work.

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Shaun6691 said:
I've actually considered that too. I just LOVE the look of the katana arm. I've looked everywhere and I can't find the pivot width listed for the katana arm vs. the rather half thought out looking gs500 arm. I saw a build thread about a guy putting on a katana arm on his 78 gs400 and it was a matter of reaming out the pivot tube through the frame and using different bearings. Now that I think about it, that sounds like a lot of work.

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Update: finally dove in head first and went for the swap. Here's a rough mock up. My question now concerns the pivot bolt. I didn't aquire the katana pivot bolt when I got the swingarm. I do know it's fatter and longer (that's what she said ) than the gs450 pivot. I was wondering if anyone knows how thick the pivot bolt for a gs500 is. I know it's pretty much the length I already need.

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Anymore news on this? Definitely interested to hear how it went.


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GS1100E swingarm on GS400/425/450

Yeah, whatever happened to this???

I'd been lusting after a GS400X chassis with GS450/500 engine and GS1100E long before I got my first GS (a GS750B), and still am lusting after the same build idea years later.

I picked up a 79 GS425E to do a similar build, figuring the 425 block could be bored for larger sleeves than the 400 block (I gotta go all our on this lil ripper... I don't want it to take the back seat to fire breathing big bore GS550/650-740cc & GS750-870cc/920cc machines that it may be parked next to, wanted to go all out and make the practically moped weight GS twin a fire breathing monster with the biggest JE or Carillo pistons I could justify having made to fit it without having them weigh too much. I have 3 MTC 920cc pistons left, they'll make a re-sleeved 400/425 into a 489cc 10.5:1. I'm sending them with the head and cylinders (porting/Serdi job/re-sleeving) to see what RapidRay the Suzuki race engine builder thinks of them vs Carillo or JE. I know the Carillo's will be way better so may go 502cc (which will also make a 944cc GS750!) or even bigger if Ray convinces me to do so. The road racer guys have said that a Wiseco 1100 kit doesn't rev up as fast as a Wiseco 1085 kit in a road race GS1000... we'll see what the verdict is.


Anyhow, I just got done measuring all of this again, and the GS400 (GS425 in my case) is about 205mm inside width. I had read 200mm on the GS400 swingarm from hillsy. Sounds about right + the thrust washers and dust shields.

I also was looking at a Zephyr ZR400C swingarm, which is aluminum and has trick eccentric axle adjusters (which are awesome to use to change the rear ride height and frame rake without having to touch the shocks, since you can spin the adjuster 180° and get the same chain adjustment but have it be on the bottom side instead of the top side of the eccentric adjuster hole).
The Zephyr swingarm is about 226mm at the pivot, however. Wider than the GS1100E even. But uses eye to eye shocks, which I have a wealth of currently (going to have to start fabricating Fox Factory Shox and Fox Street Shox GS clevis mounts...)
About 255mm between the eccentrics for the wheel and axle spacers etc.
600 mm approximate length, but I think that is end to end, not center to center of axke and pivot bolt.

I measured the GS1100E swingarms, and they are:
221mm pivot tube end to end with no thrust washers or dust seal shields.
I just measured some GS1100E dust caps and thrust washers installed on a custom cromoly Dresden style swingarm here, and they added 4.75mm width beyond the width of the inner bearing races, which also were wider than the actual pivot tube on this custom built swinger by approximately 2mm total both sides combined. So you're looking at like 228-230mm width. I will have to measure this GS750 frame here before I scrap it, it is same frame inside width as GS1100E. So we'Re looking at 5-7+mm extra to run the duse seals and thrust washers if the bearing races protrude some. I'll check on this with the swinger that has good bearings in it still. I hauled 15 -17 of these home once from a black widow infested swingarm pile in a Georgia junkyard.... bearings were all very rusted from exposure however.

20-1/8" to 21-5/8" swingarm length c-to-c depending on chain adjustment/axle position.
Around 263mm inside width at the rear wheel, without chain adjusters, which would put it right around 257mm or 258mm with the GS chain adjusters.

The pivot tube is D-shaped aluminum stock, and where the external dust seals wrap around the tube (where the actual double-lipped sealing point is), the tube is turned down in diameter to round, and smaller than the circular portion of the larger D profile of the pivote tube.

The 3 GS1100E arms I have on the shelf here all measure different depths of machining this roundvportion, I suppose only the diameter was critical, not the extent the depth of the cut was as long as it was long enough. I was hoping I could use that flat as a guide to use more crdue tools to take down the width until I was flush with the flat end from the seal area machining.
The narrowest (deepest most inboard) cut here measured at 206mm, one was over 207mm, one was about 206.5mm. Still wider than the GS4xx frame opening. So for this application, they'd have to be cut beyond the flat end of the facing machined onto them for the seal caps.

I'm thinking that some extensive work to clamp the swingarm in a big lathe cross slide vise after aligning it using dead centers on either end, and then chucking up a cutting but in the lathe jaws offset like a boring bar cuts, may be the way to tackle narrowing these accurately. I'm only beginning to become familiarized with using my lathe, but this seems to be the way, but seems like a TON of work to jig up some fixture in a cross slide vise on the toolpost deck to get the swingarm clamped perfectly in place.
I should save whatever fixture I make, as I'm sure lots of people on DTT & CafeRacer would want to capitalize on the existence of some setup like this to get their 1100E arms cut down narrower!
 

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Front view of the 1100E swinger. GS550B swinger on top, 750B below
 

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Did you ever end up finishing this? I think I am going to be setting up my 1947 Atlas MFB horizontal milling machine here this January, and I think that is the machine I will choose to use to narrow the GS1100E swingarm. I will make an offset tool bit holder sort of like a fly cutter, but use it to cut the rounded end on the swingarm in further, and then I will shave off the edges until it is the width of the GS400 / 425 frame. Heck, since I have 4 or so of these GS1100E aluminum swingarms, I will probably cut down two of them just to have a spare handy while I have everything set up.
Have to save 1 for my GS550/740 build, and another for my GS1000/1135cc build...
 
I have been doing this same swap but for a GS550 (1978). Installing a GS1100 E (1980) swing arm.

How have you figured getting around the difference in swing arm pivot? The GS550 by stock has the 14mm pivot. and the GS1100E has a 16mm.
Are you drilling the frame pivots to accept the larger pivot? Custom bearing spacers. Or do you know of a OEM bearing from another model/bike that would fit this conversion?
 
Baker72 said:
I have been doing this same swap but for a GS550 (1978). Installing a GS1100 E (1980) swing arm.

How have you figured getting around the difference in swing arm pivot? The GS550 by stock has the 14mm pivot. and the GS1100E has a 16mm.
Are you drilling the frame pivots to accept the larger pivot? Custom bearing spacers. Or do you know of a OEM bearing from another model/bike that would fit this conversion?

Make a bushing for the swingarm, run a pivot bolt that is the diameter of the 550.
 
Hey guys. Sorry to leave yall hanging for 2.5yrs! After starting this post, I bought my 1st house shortly after in February. It was a fixer upper so it's kept me busy! I got to work on the bike a few times but not any real solid progress until recently.
We ended up ditching the drum brake idea and converted to a rear disk setup using a gs1100 wheel/brake setup. Much better.
We hit a major snag when we failed to drill out the pivot bolt holes straight. That was one problem. The next was that we discovered the swing arm was twisted 1/8". So I got another swingarm and took the frame and swingarm to a machine shop to be "properly" narrowed and mated.
The machinist fabbed up new pivot pads and welded them in and got everything nice and square. So here we are. I'll throw in some up to date pics so yall can see where I'm at

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Here's a mockup from 2yrs ago before the long hiatus. What's funny is that this whole can of worms started from wanting to upgrade to r6 rearsets lol. We are fabbing a new 2-1 pipe with a sutpertrapp muffler as well. I need to find a better clevis solution to the rfy shocks. Sort of attached to running them. Love the piggyback look

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Rear setup is looking nice. Switched to a gs1100 rear wheel and a disk setup from a gs850. Rear stabilizer bar is made from 1x1 aluminum square stock

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