K75S to K75GS

Discussion in 'Some Assembly Required' started by Muddy3, Nov 7, 2011.

  1. Muddy3

    Muddy3 Muddy

    Joined:
    Mar 12, 2005
    Oddometer:
    45
    Location:
    Estes Park
    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.

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    Then this one.

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    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 scale...so far.

    A few photos.

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    #1
  2. Mr. Magoo

    Mr. Magoo n/a

    Joined:
    Oct 10, 2006
    Oddometer:
    4,980
    I love it!
    #2
  3. dpforth

    dpforth no inline fours

    Joined:
    Oct 22, 2010
    Oddometer:
    349
    Location:
    Fantasy, I mean Vancouver Island
    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.

    Cheers
    #3
  4. Muddy3

    Muddy3 Muddy

    Joined:
    Mar 12, 2005
    Oddometer:
    45
    Location:
    Estes Park
    dpforth-

    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.

    Cheers
    #4
  5. maalstroom

    maalstroom Ferret Legger

    Joined:
    Dec 22, 2006
    Oddometer:
    458
    Location:
    Laguna Madre
    Nice job! Can you show how the lights are mounted.
    #5
  6. Muddy3

    Muddy3 Muddy

    Joined:
    Mar 12, 2005
    Oddometer:
    45
    Location:
    Estes Park
    How's this? Hose clamps, brackets and a couple hitch pins.

    Attached Files:

    #6
  7. SUVslayer

    SUVslayer Been here awhile

    Joined:
    Aug 25, 2003
    Oddometer:
    957
    Location:
    Commonwealth of Massholes
    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?
    #7
  8. joenuclear

    joenuclear Planning.....

    Joined:
    Mar 16, 2007
    Oddometer:
    6,719
    Location:
    Fort Smith, Arkansas
    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
    #8
  9. MikeJansen

    MikeJansen Lost

    Joined:
    Nov 21, 2004
    Oddometer:
    132
    Location:
    Essex, UK - Still looking for home
    Awesome!

    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?

    Thanks!

    Mike
    #9
  10. Muddy3

    Muddy3 Muddy

    Joined:
    Mar 12, 2005
    Oddometer:
    45
    Location:
    Estes Park
    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.

    [​IMG]

    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.

    [​IMG]

    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.
    #10
  11. MikeJansen

    MikeJansen Lost

    Joined:
    Nov 21, 2004
    Oddometer:
    132
    Location:
    Essex, UK - Still looking for home
    Rockin'!

    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.

    M
    #11
  12. Muddy3

    Muddy3 Muddy

    Joined:
    Mar 12, 2005
    Oddometer:
    45
    Location:
    Estes Park
    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.
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    Third - A little protection for the cooling system.
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    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.
    [​IMG]
    #12
  13. Tork

    Tork Pinsetter

    Joined:
    Feb 15, 2004
    Oddometer:
    3,550
    Location:
    Duvall, WA.
    #13
  14. Tanami

    Tanami Under The Weather

    Joined:
    Mar 26, 2006
    Oddometer:
    318
    Location:
    Far, Far Away.
  15. RAGBrian

    RAGBrian jonesing for a ride

    Joined:
    Mar 22, 2008
    Oddometer:
    1,034
    Location:
    Wildwood, MO
    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.
    #15
  16. notaduc

    notaduc Adventurer

    Joined:
    Aug 3, 2011
    Oddometer:
    14
    YES! One of my favorite bikes. Always wanted to do this.

    Right on.
    #16
  17. Klay

    Klay dreaming adventurer

    Joined:
    Nov 19, 2005
    Oddometer:
    103,474
    Location:
    right here on my thermarest
    Do you worry about increased wear on the shaft drive because of the greater angle resulting from the repositioned shock?
    #17
  18. Muddy3

    Muddy3 Muddy

    Joined:
    Mar 12, 2005
    Oddometer:
    45
    Location:
    Estes Park
    Yes, it is a concern. The distance that I dropped the shock was based on a prior build, a bit trail and error and suspension sag when weighted. I've put 1500 miles on it so far. After a few thousand more miles I'll tear it down and take a hard look at the drive unit. All good at this point.

    Added some fuel capacity the other day.
    [​IMG]
    #18
  19. Canuman

    Canuman Crusty & Unobliging

    Joined:
    Jun 21, 2008
    Oddometer:
    4,674
    Location:
    The Palace of the People, VT
    That's hideous and a travesty and I really, really want one! :clap

    The K75, in my opinion, is one of the best BMW ever made.
    #19
  20. Just Dan

    Just Dan Bugger, Burnt toast

    Joined:
    Jun 7, 2006
    Oddometer:
    1,917
    Location:
    Hobart, Tasmania
    There growing. This one was built about 10 years ago

    [​IMG]
    #20