1980 GS1000 restomod

[80GS1000]

How similar is the frame of the 80GS to a 84 1150E? I'm curious as to how difficult the suspension conversion was, was it a straight swap or require minor mods? Up to now I've only been looking at early 90's GSXR for a suspension swap I didn't think the 2000s Gsxr's were in play.
I've similar plans for my 84 but at this point I'm still gathering data in order to know what parts/donor bikes I'm looking for.
Fork length is a definite problem.

As Dan mentioned the frames are totally different. For the front end on mine, I used a set of conversion bearings (check out All Balls Racing) to bolt on the GSXR 1000 triples. The neck of the frame required welding on some new steering stops.

Once the GSXR front end is bolted on, you need to address the fact that late model GSXR forks are much shorter than GS forks, which can lead to ground clearance and handling issues. I plan on adding some fork cap extenders soon to address this and raise the front ride height 20-30 mm.

The stock GSXR 1000 fork springs were too soft at 0.85 kg/mm so I swapped them out for 1.0 kg/mm Racetech springs.

On my GS1000, the stock speedometer drive was on the front wheel, so an aftermarket speedometer is needed.

Also GSXR front ends run clip-ons stock, so if you want to use regular handlebars you need a handlebar conversion kit like the one I use from Spiegler or potentially drill/tap the upper GSXR triple clamp for handlebar risers.

[80GS1000]

Rear wheel chassis and chain alignment


One of the goals of this revision to this build is to get the rear wheel chassis and chain alignment as true as possible for optimal handling and chain/sprocket wear.


In the previous version of this build, a 2005 (K5) GSXR 750 rear wheel was used in the 2006 (K6) GSXR 1000 swingarm. Rear wheel chassis alignment was good with this wheel as the bike steered straight and true without any pulling to the side. Chain and sprocket alignment was not so great with this wheel however as the assembled wheel hub and sprocket carrier were about 10 mm too wide. To combat this, I had the sprocket carrier posts machined down where they contact the rear wheel hub and shaved the cush drive rubbers to bring the rear sprocket inward. This improved the chain run but in turn caused another issue because now the taper on the posts on the back of the sprocket carrier no longer matched the contours of the wheel hub, causing some good old fashioned metal on metal contact, chowdering the hub.


Ugh. No bueno.







On the bright side, the K5/K6 GSXR 600/750 rear wheels have the same 28 mm axle diameter, 220 mm diameter rear brake rotor, are both 5.5x17", and even use the same wheel spacers on the brake and sprocket side of the rear axle. The crucial difference is that the stock, unmodified K6 600/750 wheel is about 9-10 mm narrower at the sprocket carrier/wheel hub than the unmodified K5 wheel.


So, for prototyping purposes, I bolted up a spare damaged (bent lip) 2006 GSXR 750 rear wheel I had on hand into the K6 GSXR 1000 swingarm. It bolted up easily since the axle/spacer/brake rotor dimensions are the same.


Then I started checking alignment chassis and chain alignment using this K6 750 wheel.


The old rear tire currently mounted on this spare wheel is 225 mm across, as measured with a soft tape measure going across the tread from one edge of the sidewall to the other. I marked the tire at 112.5 mm and then shot a crosshair laser level pointing at that mark to see how it lined up with the center of the backbone of the frame.


Excellent Smithers, excellent.





Then, because lasers, I checked the chain alignment. Also looking good. I'm using a 5/8" offset 520 pitch front sprocket, a DID ERV3 520 chain, and Vortex K6 GSXR 750 520 pitch 48 tooth rear sprocket in this setup. IME, 5/8" is the maximum front sprocket offset you can run in a GS1000 frame with a 520 chain before the chain rubs on the frame.





Because of the width difference between the K5 & K6 GSXR 750 wheel hubs, there is now a gap between the sprocket side spacer and the swingarm. I'll need to get a new sprocket side spacer made up to fill in the gap. I also ordered a used, good condition K6 GSXR 750 rear wheel to replace the damaged one used for prototyping.

[salty_monk]

Looking good... nice to see the plan coming together

[80GS1000]

CAD drawing for the needed M28x39x30 sprocket side spacer. Now just need to find a shop who can CNC this simple spacer from some 6061 aluminum without charging a kidney as compensation. Any ideas?

[80GS1000]

Welp, the online and local machine shops think that one-off CNC machined aluminum spacers are worth their weight in gold, so another solution must be obtained.

The stock K6 GSXR 750 sprocket side spacer is M28x39x17. I need a M28x39x30 spacer. If a machinist turns down a spare M28x39x17 stock spacer by 4mm in length, then I should be able to stack the stock and modified spacers next to each other to get the spacing needed. Thanks to Salty_Monk for the discussion on this topic offline.

[storm 64]

Welp, the online and local machine shops think that one-off CNC machined aluminum spacers are worth their weight in gold, so another solution must be obtained.

The stock K6 GSXR 750 sprocket side spacer is M28x39x17. I need a M28x39x29 spacer. If a machinist turns down a spare M28x39x17 stock spacer by 5mm in length, then I should be able to stack the stock and modified spacers next to each other to get the spacing needed. Thanks to Salty_Monk for the discussion on this topic offline.

Shoot me a private message, I might be able to help you out. 👍

[80GS1000]

Shoot me a private message, I might be able to help you out. 

PM sent. Thanks!

[salty_monk]

Shoot me a private message, I might be able to help you out. 

I thought you might show up on this if PJ put a thread out there...

[storm 64]

No problem, I'm always ready to help a fellow GS'er out. 👍

[80GS1000]

Need some opinions please on cosmetics:

• Black out the forks? The gold forks don't jive with the rest of the bike IMO. Considering having them reanodized black.
• Install the side covers? The Yoshimura GS1000 racebike (one of the inspirations for this build) didn't have them, but I'm leaning toward reinstalling them to give the bike a more "finished" look.

[Nessism]

I recently purchased a small lathe and could whittle you out a spacer if you haven't found someone else to do it. PM me as needed.

[steve murdoch]

From the sounds of it you are going for a resto-mod look. I prefer the look with side covers in place.
If it was a lightweight cafe theme ditch the covers and show off the empty spaces.

If there is no other gold on the bike, black out the forks.
What wheels are you using?

[80GS1000]

I recently purchased a small lathe and could whittle you out a spacer if you haven't found someone else to do it. PM me as needed.

Thanks Ed.

[80GS1000]

From the sounds of it you are going for a resto-mod look. I prefer the look with side covers in place.
If it was a lightweight cafe theme ditch the covers and show off the empty spaces.

If there is no other gold on the bike, black out the forks.
What wheels are you using?

Using the wheels shown: black 3 spoke GSXR wheels from a 2004 GSXR 1000 in the front and 2006 GSXR 750 on the rear.

[80GS1000]

Adios 2019 riding season...what's this cold, wet, white stuff on the ground this morning?

I think we skipped fall this year. Supposed to get down to 10 degrees F on Tuesday night and then 13 degrees F on Wednesday night.

Just means wrenching season is ramping up though...