GS1100GK 41mm fork slider bushings? upper bushing below seal not in fiches even?

[Chuck78]

It seems as if the lower fork glide bushings for the bottom of the upper tubes (the "piston" as the fiches call it), for the GS1100GK have been discontinued. I've torn down a pair that has no rust on the chrome and would like to rebuild them with new seals and glides/bushings, but cannot find any of these even NOS.

Has anyone found something to substitute for these from other 41mm forks?

[Chuck78]

It's part #2 in the fiche diagram. The other upper glide bushing goes directly under the fork seals and inserts inside of the aluminum lower outer fork tube, so the upper chrome steel stanchion tube glides through it. This is not shown whatsoever on any fiches for the models I've looked up (various 1100's, 650's, 750's). On the 650 & 1100gk forks on my bench, there is clearly an identical internal bushing that is a mirror image of the slightly smaller lower glide bushing shown in the fiches as part #2 "piston." The upper glide is slightly larger & has the internal friction lining & mounts internal to the fork lowers. The lower #2 glide bushing mounts external on the bottom of the upper tubes and has its friction surface on the outside.

These GK forks are really nice, great chrome, & very stout, but I don't want to track down a triple clamp set, buy racetech emulators & tarozzi fork brace for a fork that I can't get new bushings for.

[Chuck78]

Top is the 1100GK upper/inner stanchion tube and the lower glide bushing area. Below that is my GS650G with a noticeably much thicker glide bushing (I just replaced it 3 years ago). I now recalled upon dismantling the 650 forks the other day & a few years ago when I first got them with the original guts, that the bushings interfere with each other, and you cannot dismantle this type of GS fork (80-82 introduced these upper & lower glide bushings) without sort of slide-hammering the upper stanchion out of the lowers, which in turn pops the upper bushing and fork seal out if the lowers, as the lower bushing's o.d. is larger than the upper bushing's i.d. by nearly 1mm overall.

Disassembling the GK forks by just popping the uppers out of the seals/lowers without the interference that even the un-rebuilt 30,000 Mi GS650G dual disc forks had on initial teardown (upgraded the 77 750 to those forks for dual disc) confirms that the below photo is showing a very worn lower glide bushing at the bottom of the upper tube as witnessed in comparison to the 35mm gs650g bushing as installed right next to it. Major bummer Suzuki...for making this bushing on these collosal forks obsolete.

[Chuck78]

The local vintage Japanese mc junkyard told me they have a giant shrink wrapped crate of GS1100GK parts that were less frequently requested, but its buried under 5 more palletized crates. I am thinking that maybe I could have better luck with another set & maybe even jb weld an aluminum beverage can shim to the insides of the lower bushings on a less worn pair, and maybe that would rejuvenate them for many years to come? The upper bushing looks substantially thicker and less worn luckily, since they were never available according to the fiches and could not be shimmed since they have no real split to expand/contract them.

Honestly, its obviously worn, but as I assembled them and compared wear & play, the gs1100gk had only the slightest but more slop/play with the upper inserted into the lower in the normal operating depth compared to the gs650 with newer bushings and a lower that is 36mm o.d. ( 1mm larger installed o.d.) on the 35mm lower.


The 1100gk bushing's installed o.d. was just a very marginally larger amount (0.12mm)than the 41mm upper tubes' chromed area, however I just now realized that the GK's upper fork tube's bottom end is for some reason machined down very slightly less than the 41mm o.d. nice smooth chrome section that the upper bushing and seal ride on for about 3.25" above the top of the lower bushing. Hmmmm I wonder if this is a design difference affecting bushing size compared to the 650 forks??? My finger is pointing at the slight step down ridge, and the surface below(left of) it has a grooved turned-on-lathe texture to it.



I now looked back at the upper bushing in the lower fork tubes and recalled that the top 3" or so below the bushing WS machined out in the aluminum what looks to be about .3mm larger i.d. than the center & lower portion of the lowers, similar to how the bottom of the uppers was machined.

I wish the darn factory service manual had specs on bushing thicknesses!!! They just tell you that the bushings will be damaged on removal, and to just replace them.

[kingofvenus]

Wonder if one from a 1st gen gsx600f/750f would work, they have 41mm tubes.

[Chuck78]

My calipers only go to 150mm, but when I was at the junkyard, I realized sv650's had nearly identical spacing at around 204-205mm. The GK is 204. This is critical for the brake calipers to align properly, & for the Tarozzi fork Brace to fit that is made for the GK.

On the Tarozzi fitment charts, I noticed the Kawasak z1300 had the same clamping dimensions but 210mm spacing, and also noticed GSXR1000 triples at the yard that looked to be around 210. All of these triples (I forgot to look at the parted out z1300) had very little offset however, which will take away substantially from the trail measurement, and decrease high speed straight line stability and have a slight decrease in the wheel's leverage on the road in cornering traction, but will give it very quick turn-in (that may require a steering damper to make 100% rideable).

The bigger issue is investing in a fork that has no replacement bushings available... Still hoping for a source for a retrofit

[bwringer]

Racetech makes and sells bushings. No idea whether they will have some the correct dimensions for your forks, but there's a chart on their site:

http://www.racetech.com/HTML_FILES/FMB-ForkBushings.html

If you can get them to respond to an email, you might send them the dimensions of the bushings -- they likely won't have a listing for such an obscure model as the GK.

[Chuck78]

You the man Brian! now I just need to take them back apart to measure them & see if RaceTech makes anything in that size. I gave up on em & reassembled loosely & shelved em... If I can get bushings, then I may run them instead of VTR1000F Super hawk full cartridge forks, or at least put em on my next project bike (looking to buy up cheap project 77-79 gs750's/77-82 GS550's/GS650E's/GR650X's to rebuild & push to friends who want bikes)

Thanks!

[londonboards]

You can still buy these bushings (part no. 51121-49200). I got some from my local Suzuki dealer a month back.

[bwringer]

You can still buy these bushings (part no. 51121-49200). I got some from my local Suzuki dealer a month back.

These are the bushings used on the 37mm forks on all other shafties and many other models besides. The OP has a GS1100GK, which has larger 41mm forks.




I am sort of wondering, though... there are many other motorcycles with 41mm forks. For example, I've had a couple of VX800s (which used 41mm forks), and this bushing "slide metal" is available and listed.

That seems like a last resort, though -- with only the same ID (41mm) you can't tell whether the other dimensions will be the same.

[Chuck78]

Well I am on the fence about these, but if I can get some bushings sourced, I could have 41mm forks with racetech springs & emulators, Tarozzi fork brace, & retain my custom twinpot brake setup (modded the ninja caliper brackets to fit gs forks without adapters, & look bone stock aside from the cbr900rr floating rotors). That'd be a rebuilt& modded investment of about $450 for 41mm stick looking forks.

The other options would be get another set of GS1000 forks & 1100 triples & do the same treatment... Or:

Get 97-06 Honda VTR1000F SuperHawk forks, $400 in racetech compression cartridges & rebound cartridges + springs, + $120 in Honda rebuild parts & a few special tools for the cartridges, + $300-ish initial investment in the forks. Then I'd get 41mm externally adjustable dampening & preload true cartridge forks that will actually be on par with the deCarbon style rear shock technology that we can bolt on our bikes for $500-700+

Add to that the extra expense of Superhawk 4 piston calipers & a second set of cbr900rr or cb600f "599 Hornet" rotors, as this type of Honda 296mm rotor that I already run is exactly what the superhawk forks were designed to run, & will actually make full use of the rotor friction surface, as the ninja/gs500 calipers only use the upper 85% as they run shorter height pads.

The superhawk setup will definitely be on par with my rear setup of gs1100e swingarm & either Fox Piggyback or YSS Piggyback shocks, & wy wider alloy rims & super sticky 140/70-18 & 110/80-18 Shinko or Pirelli tires of choice. Mild frame bracing will be added as well on the next teardown.

Where to draw the line??? If I run the superhawk front end, the gs425 502cc racer project can get the 35mm rebuilt gs650 forks & twinpot brakes, but I was really originally planing to make a 37mm gs500 fork/caliper/RT emulators & single 310mm cbr900rr front rotor setup to save weight. Decisions...

[Chuck78]

The superhawk front end would basically cost a little more than double, at $1000 completed, but would end up as the ultimate front end for our bikes. Stock they are good but the rebound dampening isn't perfect, and the springs are soft of course.

[Chuck78]

FMBI 412015 P FORK BUSH INNER-41x20x1.5 PAIR

From memory & approximate estimation visually of size, I think this $39.99 set of fork glide bushings from RaceTech will be the likely fit. I left my calipers at a buddy's house & haven't torn forks down again, but I will confirm this and check on the outer bushings as well. Thanks again, Brian

Chuck

[Camicus]

I just rebuilt the forks of my 1982 Suzuki GS1100GK and it was quite the ordeal to find the right bushings because no one including Suzuki knows what they are.

The outer bushings are easy to find and can be purchased at Racetech (link provided below) and are part FMBO 41122 P (Fork Bush Outer-41x12x2 PAIR).

The inner bushings are not made anymore by anyone I could find due to the lack of demand for this rare size. The inner bushings are FMBI 40201 P. I lucked out and found a pair on Ebay that someone had hung on to but never used. If you can't find a set of these rare bushings, I would use FMBI 39201 P and just have a machine shop increase the diameter if need be.

http://www.racetech.com/HTML_FILES/FMB-ForkBushings.html

Cam

[Chuck78]

Wow cam, I missed your edit update on this... thanks a lot!