1991 BMW K75S - Cafe Racer Build - Page 4
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1991 BMW K75S - Cafe Racer Build

This is a discussion on 1991 BMW K75S - Cafe Racer Build within the Project Builds forums, part of the Caferacer.net Forums category; Plan on spending the next week thoroughly going through and finally finishing the build. Over the bit of downtime I've had, I've relocated the Shorai ...

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Thread: 1991 BMW K75S - Cafe Racer Build

  1. #31
    Junior Member almostordinary's Avatar
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    Plan on spending the next week thoroughly going through and finally finishing the build.

    Over the bit of downtime I've had, I've relocated the Shorai battery, created a metal seatpan that I attached the ECU to, and doing some more cleanup with the overflow tank and rear brake reservoir.

    Tidy'd up the front end, thread locked everything (blue), and wired up my motogadget motoscope mini, as well as some motogadget pin lights. Added additional side turn signals flush mounted into the holes on the tank as well.

    Redid the entire fuel system (Sending unit, pump, filter, new bosch injectors) as well as the ignition system (plugs/wires)

    Next up is getting the timing buttoned up, put the bottom flare back on, wire and mock up rear running/brake light and motogadget pin turn signals and take her on her maiden voyage.

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  2. #32
    Junior Member almostordinary's Avatar
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    Finally got some more time on my hands and finished up a ton of wiring and cleanup.

    Just need to tackle the seat and ver1 of this bike will be on the road. Going to change up the wheel color but that's for another time. Can't wait to finally ride!

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  3. #33
    Senior Member TrialsRider's Avatar
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    Something looks missing :/ fenders maybe?

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  5. #34
    Senior Member XB33BSA's Avatar
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    well the front tar will just clear the lower yoke considering 7.3 '' fork travel
    if you must lower the front a huge amount you need to do it by shortening the fork travel
    the problem is depending if you lowered the rear or not is the trail number
    the k75 is older school rake angle which requires a heay offset in the yokes to yank the bike into a sweet treail number
    if you must have the bike dragging metal in the corners then one of 2 things to avoid spontaneous instabilitry
    a good position sensitive steering damper or a top bottom yoke sdet with LESS offset
    take a look at anty sportbike mid 90's-on the have steep as fook head angles 24 is common as little as 23.5
    you are stock at 27.5
    the steep fork angle requires much less offset to maintain a trail number within the sweet spot
    do not underestimate small changes it has only taken 100+ years to figure out that a motorcycle only works in a safe good handling manner within an extremely narrow range of trail
    you sound intelligent so i can only suggest some simple measurements
    first get an adjustable zero bubble protractor level
    or a machinists protracter with bubble that fits the machinists rullers
    find level concrete or asphalt
    most floors in a garages is not level ,it will be pitched slightly out the main car entrance door
    remember tiny changes make a difference so you must be sure of the angle that the tirtes are resting on
    it is really best to put the bike on a heavy 2x6 or better and block and shim it untill it is perfectly level
    this eliminates errors in resetting zero on the bubble for a slopped surface
    i have heard of others that simply measure the head angle against having the frame engine cradle lower tubes as zero bubble
    they feel that mfg's universally make frames with the lower tubes at earth zero level \
    i call HORSESHIT on that
    using logic it must be measured the way i promote gently topped out
    that is the only sitution that is solid enuff to go by
    once that is done support the bike in the middle and raise it up untill the suspension units JUST reach a topped out situation
    the front has top-out springs so avoid getting into that zone
    getting into top-out sprngs will give a number on the more stable side leading into perhaps too much stability removed upon set up
    there is no replacement for careful test riding
    i can even out line how to induce instability if you are into that
    i am because i have a personality that is unstable as well ,at times
    IF you already have the with rider and without rider sag/balance set up you can just let the bike settle without topping out the suspenders but it stilll leaves too much room for dodgy numbers as the suspensin and any pivot points should be warmed up and confirmed of stiction-free travel
    doing it as i promote allows a very accurate measurement of head angle and trail
    which then finally and just as important is to determine if you have the correct spring front and rear this getting the balance correct on springs can transform a motorcycle like magic.srioiusly it is the single most effective handling and ridability upgrade you can do to any motorcycle and have it make a difference ,sometimes completely transforming the bike from an unhappy sick dog into a limo ride full of red headed hookers and cocaine .
    the only reason todays ipad infected in the brain drones dont delve into...first it involves actually riding a motorcycle with skill....or even riding at all ever
    it is that it cannot be shown in an image in there gadget... so its a feel thing
    and will not cost a ton of money
    if you think any friends will be impressed uh uh that dog wont hunt
    back to measuring
    next make sure that the front wheel is directly inline with the rear
    then with the protrator deal lay it on a fork stanchion tube
    there is ample room between bottom yoke and seal wiper
    make sure the base is not twisted out of the vertical p[lane
    oh yeah make sure the bike is exactly vertical put that in way above in setup

    also make sure the protractor rotating section is pointing straight ahead
    boom you have head angle
    in my opinion the most accurate way to then get trail is to measure the exact youke off set and the exact tire actual diameter and use an online calculator
    trail numbers 3.5 - 4.25 is my opinion stay closer to 4
    anything under 3.5'' trail can be deadly depending on weight distrabution frame flex tires a million things
    but a low number without a damper is a fools mission
    i have my homebuilt adv bike set up so that it feels a tad nervous if you let it at 60 pluss mph
    my only and best suggestion is do not go very much shorter on trail than the k75 has stock
    srsly this is no joke it is literally a life and death deal that is getting it too far wrong
    read this at least down the p[age when they talk about the oem changing geometry https://motorcyclespecs.co.za/model/..._gpz550_81.htm
    i picked it out because at the time the lil 550 was just about the best handling sporty bike ever built
    coincidently the yamaha 550 was just about as good
    the specifications i am sure garnered from its big brother,the last of the real superbikes when they had a bassis on a oem machine , ridden by a couple unkown talent less riders lol
    hard to remember their names rawson and lainey ?
    and just to throw in something cool i obserrved closely and actuially built parts for this truly national caliber superbike back in 1980-82

    so i know a bit ,am not making anything up its just a memory that holds this info,like a vault ,...from experience ,but, from mostly reading ,
    god help me if i try to remember where my other tiva sandal is lol
    Last edited by XB33BSA; 08-19-2019 at 02:16 PM.

  6. #35
    Junior Member almostordinary's Avatar
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    Quick update.

    Had her out a couple times over the last two weeks... super slammed on a new film project, but she's getting a good shake down and I'm loving how its going.

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  7. #36
    Senior Member TrialsRider's Avatar
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    Zoooooom


    lol bit like riding a car engine, ain't it

    oh wait, you have the 3 cylinder
    bit like riding a seadoo ain't it

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