gs1100e swingarm conversion swap to my 78 gs400x

[Chuck78]

Here is the wonderful write up that John did about the gusset added to the gs450 frames that was missing from the gs400/425 frames & is why they twist in the front in hard bumpy cornering:

http://www.thegsresources.com/_forum/showthread.php?231838-GS400-450-frame-reinforcement

My machinist friend looked at some photos I sent but said he'd really have to see one in person to tell me what it'd take to jig it up to run in a mill. The vintage Japanese mc junkyard only had 2 swingarms on bikes that aren't likely to get parted out. My buddy has one tucked away for his kz1000, but he's uncertain the extent of mods he'll do to it now, especially needing a new can chain tunnel o-ring and the top end torn down (head gasket/base gasket while he's in there).
He might sell that to me, but not certain if he is/isn't going to use it. There are a few for sale online & eBay, but summer opening prices get inflated to $200+ on evilbay. I'm sure a forum member may come up with a spare sooner or later. As I read elsewhere, "makes ya wonder what keeps happening to all these poor GS1100E's that the swing arms keep popping up for sale and swapped onto all kinds of other bikes!"

[Shaun6691]

Not to raise the dead but did anything become of this? I ask because I have an 82 gs450 that I'm wanting to do this to. I even have the gs1100e swingarm already.

[Chuck78]

Larry decided he was too tall for a GS400 & is sticking with his Harley Choppers after throwing a rod through his GS1100E crankcase. He sold his GS400 project.

I am pursuing this swap, however.
It may be a while as I have a gs550 (740cc GS650 top end)resto-mod rebuild ahead of it for the wifey, & 2 or 3 friends' bikes to mechanically/electrically refurbish.

You'll need to basically mill off the rounded ends of the swingarm and convert to Kawasaki Zephyr style swingarm dust seals and hardware, but using a GS type bearing and races. You'll need to have a machinist bush the gs1100e inner races. You can get the bearings brand new in the gs1100e o.d. and i.d. and in the stock width and narrower widths.

So you have the options to either bore the bearing register deeper into the swingarm and narrow the center spacer, or run narrower bearings than the 1100E and narrow the center spacer. Perhaps with the gs450 inner spacer, maybe you need not narrow that any and can run the gs1100e inner races

[Chuck78]

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 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 dust 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.

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. ( all three swingarms here measured a different inside width)






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 round portion, I suppose only the diameter was critical, not the extent the depth of the cut was as long as it was long enough for the seal cap to fit. I was hoping I could use that flat as a guide to use more crude 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!