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Muddy3 11-07-2011 07:32 PM

K75S to K75GS
Truth is I'm much better at window shopping Toxic Britney in Jo Momma than I'll ever be at writing a Build Thread. So just one ground rule - Keep your expectations low and I'll try to over-deliver.

Here is where the problem started...I saw this picture.

Then this one.

I knew a little about these, having owned a K75C back in the early 90's. I remembered it as smooth and pain free to own. For this project I found a one owner, well maintained 1992 K75S with 26,000 miles, less than an hour from my house. Just $3300 later, I had myself a project.

Don't expect a lot of "before pictures". BMW made 10's of thousands of these things...we all know what they looked like. Besides, I hate having evidence of failed ideas around for my wife to use as evidence.

The Build:

The rear wheel was the crux of the project. From what I could gather, most of these conversions used either a R100GS drive shaft w/drum brake or started with the C model w/drum brake. I wanted to keep the disk brake and go with a spoked wheel. Clearance between the caliper and spokes was the issue. Lucky for me Zach at Woody's Wheel Works solved the issue with a different model caliper and rotor. I'm currently using the rear Progressive shock that came on the bike with the upper mount repositioned down to raise the rear of the bike.

Front end is a 45mm Marzocchi Shiver and triples off a GasGas FSE450...FleaBay find. A 1" spacer below the top triple and this thing bolt right on...sort of. Baja Designs dual 8" lights that were sitting around the garage and a new Pro Taper bar finished off the front end.

Exhaust- Kept the 3 into 1 and had Collins Muffler in Loveland bend up a pipe to connect the silencer. The silencer is a Delkevic oval shortened 4".

Center stand - lengthened 2 inches to deal with the longer suspension.

The Ride - My experience is limited to 100 miles so far with about 20 of that gravel and/or easy fire roads. Got to say I'm pretty amazed to this point. It's no 950SE but it has no trouble getting out of it's own way. Still some sorting to do with the suspension but we're not too far off. Needs a skid plate and maybe some engine crash guards.

As projects go this was a 4 on the 1-10 difficulty far.

A few photos.

Mr. Magoo 11-07-2011 07:43 PM

I love it!

dpforth 11-07-2011 07:48 PM

That bike is just effin awesome, great job. :clap What rear hub did you end up using? Just bolted on?

I had a K75 for a little while but someone else wanted it more before I finished it.


Muddy3 11-08-2011 07:46 AM


The rear hub is from an 1150GS. The rim is a 17" running a 130/80 - 17 TKC80. It is a direct bolt on, as long as you use the 1150GS rotor and caliper then offset the rim from the centerline of the hub a bit.


maalstroom 11-11-2011 04:34 AM

Nice job! Can you show how the lights are mounted.

Muddy3 11-11-2011 08:15 AM

1 Attachment(s)
How's this? Hose clamps, brackets and a couple hitch pins.

SUVslayer 11-11-2011 08:22 AM

Very cool. And pretty unique. Can't say I've ever seen a GS'd K bike. Me likes!
IMHO, hose clamps to hold all those lights seems a little (lot) weak, esp if you're planning on any off roading fun beyond fire roads. I'd think about beefing that up with a solid bracket.
What's the rear shock?

joenuclear 11-11-2011 12:18 PM

Looks like the same clamps on the original photo. Rick Stator sent me the same ones for my dual 8" headlight set-up. I sold them to some guy named Doug who rode the across some place called Russia. I think they'll hold up.:lol3

MikeJansen 11-14-2011 04:50 AM


I am looking for a K75 atm partially because of you and your build. I would love to know more about your front fork set up. You mention that they are 45mm Marzocchi's off a GasGas.

Did you use the yokes from the GasGas too or did you modify the BMW parts? Also is that the GasGas wheel mounted up front?

One last thing for now, could you show the lowered shock mount?



Muddy3 11-14-2011 06:55 PM

I used the triples from the GasGas. The backup plan was to have a custom set of triples made for these forks. A quick Google search brought up a guy out east that would make up a set of triples if needed.

Below is a photo of the lowered shock mount. It consists of two pieces of steel plate bolted to the original shock mount hole and the unused hole in front of the shock. The shock is the Progressive one on the bike when I purchased it. Not as much travel as I originally wanted in the rear end...but works surprisingly well so far on the gravel and fire roads.

Also note that the original red side panels are back on the bike. I made brackets with rubber grommets to hold the rear of the panel. This rear side panel mount, normally slides into the tail piece bodywork, which is now gone.

Added tank knee pads, and a skid plate to the sump over the weekend. Also replaced the crankcase breather, which was cracked, go course.

Next up are dirt bike foot pegs. I'm open to great suggestions and ideas.

MikeJansen 11-14-2011 11:29 PM


Thanks for the pics and the information!

Now I just gotta find a good K75S to start with :nod

Some days I wish I was back in the states. . . . parts here can get frighteningly expensive.


Muddy3 12-01-2011 07:10 PM

Finished a couple of upgrades;

First - heated grips. Bike came with a socket for the electric vest, now the hands will be toasty too.

Second - IMS pegs.

Third - A little protection for the cooling system.

Last - Tail rack and new brackets. 3/16" ABS plastic bent up at both ends with a few holes drilled for straps. The new brackets are fabricated from steel sheet and attached directly to the frame tabs. Pretty solid...I stood on the rack the other night...all 215 lbs and it barely flexed. Rack should fit a Rotopax fuel tank about perfect for some extended range.

Tork 12-03-2011 05:32 PM


For those who are looking for a starter bike for GS treatment,

No affiliation:deal

Tanami 12-05-2011 02:35 AM

just stumbled across this muddy....
thought you might appreciate it..

RAGBrian 12-23-2011 10:10 PM

Nice project! :lurk Subscribed to watch this evolve. I need to keep an eye out for a future K bike - I always have wanted one, now it looks like I should get one and think about doing the same mods.

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