K75GS by Tartiflat

Discussion in 'Parallel Universe' started by JBT, Aug 17, 2015.

  1. JBT

    JBT Adventurer

    Joined:
    Feb 22, 2011
    Oddometer:
    12
    Hi there,
    I'm not often here but as I sometimes saw pics of GS conversions on BMW K75, here is mine, juste finished:
    [​IMG]
    [​IMG][​IMG] 20150807_204812.jpg
    The purpose was not to make another off road monster bitza but to build a K75GS that BMW could (should) have done and commercialized in the mid 80's, using nothing but original parts, melting the qualities of the K75 ( smooth, reliable, highway proof, comfortable for pilot and passenger) with the GS ones ( off road aptitudes, easy and efficient on mountain twirling roads ( I live in the French Alps).


    The base is a '85 K75C, with 100k kms, the engine was overhauled. A K1100LT gearbox, paralever and bevel drive, with the K11 shock, drive a R1100GS wheel. I first planned to fit a R100GS bevel on the K11 shaft, and use a R100GS wheel with drum brake, but that would need machining, the R100 intake shaft beeing longer than the K1100 one. So the R1100 rim is a bit wide at my opinion, visually.
    The front end comes also from a R100GS, but with a twin disc brake, using a right slider machined to fit the left stanchion and wheel axel to provide its fixings for the extra caliper. Calipers, discs and master cylinder are still the K75 equipment, as the drilled discs save weight compared to the plain surface of the R100GS disc.
    The headlamp carter is cut to fit the original K75 instrument cluster above, hiding between the GS windscreen and bars.
    The seat receives a new foam and cover, referring to the original R80G/S pattern, with the Alpinwhite paint sprayed on the body.
    The exhaust is stock, that allows to keep the saddlebags mountings in place and my ears in peace. I don't expect to ford rivers anyway. But who does really?

    After 18 months building, it now runs fine...handling is great on the road, as my R100GS is, but with a better frame rigidity and better brakes. The main difference is about the engine character, the K75 gives its best after 4500rpm, when the R100 is better under that, but the 15 extra HP allow to ride pretty fast. I've not really tested it off road yet, but that will come.
    The reactions of people seeing that bike in the middle of the others in the workshop makes me thing that the goal is attempted: they don't notice it at first: "Oh, you have R1100GS...and an R100GS Paris Dakar, great! And a K1, wahou! And a R100RS..."etc. Then "Oh, and this is a...no, it"s a...but...no? Yet it has...But it's a...with a?! Er, tell, what's this model exactly, I never saw it?"
    #1
    madefrtv likes this.
  2. Warin

    Warin Retired

    Joined:
    Aug 30, 2012
    Oddometer:
    14,947
    Put a sump guard on it! 3mm thick aluminium sheet bent up or wielded to fit . You need to protect the water pump .. and the sump it self.

    You will not have lost any weight.... The K11 rear will not have given you any increased travel? You may obtain more travel if you are carefull with the drive shaft U joints binding.
    The fuel consumption should be better than the R100GS.
    The standard exhaust is fairly good.

    At the moment I'd call it a K75GS .. not a K75G/S. A G/S would be lighter with more suspension travel.

    -edit - the rear indicators will get damaged in a fall ... replace with something generic and cheap.

    Enjoy. But put a sump guard on it before you damage something.

    --------------------
    I'd like a K75 motor with 4 valve and full motornic EFI.

    Is DeerSlayer still around?
    #2
  3. malloy

    malloy Long timer Super Supporter

    Joined:
    Sep 25, 2006
    Oddometer:
    6,388
    Location:
    SOUTH OF THE BORDER
    SWEET!
    #3
  4. euromotorcycles

    euromotorcycles Been here awhile

    Joined:
    Dec 21, 2007
    Oddometer:
    170
    Hi JBT,

    Nice work.

    How do the front and rear wheels line up with the K1100 paralever final drive and R1100 gs rear wire wheel. Does the rear wheel center in to the front one or do you need to shim or re-lace the rear wheel with a different offset to get them centered.
    #4