K75 Question

Discussion in 'Old's Cool' started by ericrat, Mar 22, 2012.

  1. ericrat

    ericrat Long timer

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    I am working on my wifes '91 K75RT, about 50,000 miles . If it was MY bike, I would just plough right into it, but since it is HER bike, I figured I better double check myself with the wise denizens here.

    She has had trouble with stalling at stop lights. Presumably when warmed up. Also reports increased use of the "choke" for starting and needing to leave it on longer than in the past. Fuel and air filters were replaced last year, inside of the tank is spotless.

    I don't know if it has ever had a valve check and adjustment. I am going to do this first.
    Valve adjustment questions:
    I am planning on making the tool detailed here: http://www.ibmwr.org/ktech/k100-8v-adjust-tool.pdf . Anyone have a better suggestion? I don't see that anyone sells the tool, i.e. Cycleworks, etc. It appears the "holder" could easily be made out of aluminum. How about the prying tool? I have some 1/4 inch 6061 plate that would be perfect to cut out with the jig saw. Too soft?

    It appears the valve shims are 29mm. I don't have a dealer near me. Can I use Kawasaki shims? If I use KLR parts will the world explode?

    Is there really no way to check dynamic timing? The Clymer procedure with a dial indicator is rather... two strokish.

    Lastly, outside of double checking vacuum lines, etc any other suggestions for a stalling bike that runs fine at speed?

    Thanks :wave

    Eric
    #1
  2. MightyChosen1

    MightyChosen1 I wanna be sedated

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    I had similar problems with my k75 years ago and it ended up being the throttle posistion sensor was out of adjustment. I cant remember the procedure but it only takes about 5 minutes.

    I think I still have a K bike manual out in the garage if you cant find it on the net.







    .
    #2
  3. Paul Mihalka

    Paul Mihalka Old Fart

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    Check the rubber crankcase breather hose. If split, it would do just that.
    #3
  4. OldPete

    OldPete Be aware

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    Check the cam lobe clearance first as it may be OK.
    These engines hold adjustment very well and for a long time... Gotta '91 K75s.
    #4
  5. Zagando

    Zagando BMW uber alles!

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    Tiny little Z-shaped hose kind of between the battery and airbox; they get old and brittle and thus crack easily.

    Btw, there's a guy who makes and sells the valve adjustment tools a lot cheaper than BMW's; do some searching (BMWMOA site or the IBMWR site should turn up his name and contact info) if you ever need a set.

    Good luck with sorting her out but hopefully it is something really simple as others have pointed out.
    #5
  6. bmwrench

    bmwrench Long timer

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    The bike is probably running lean. This can be caused by air leaks, as others have suggested, throttle bodies out of synch (if one cylinder has lower vaccum, there's no way for these bikes to compensate), low fuel pressure, or the need for an idle mixture adjustment.


    The K75 doesn't have a TPS; it has a switch which causes injection duration to drop off when the throttle is closed while decellerating and another switch which causes more injection duration at 3/4 throttle and up.

    You don't need the picking/prying tool at all to remove valve adjustment shims. The best tool for this job is a blow-gun. Put the tip of the blow-gun into the slot in the lifter bucket and pull the trigger. It'll pop the shim out.
    #6
  7. ericrat

    ericrat Long timer

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    You guys are great. Sure enough, the hose is cracked on the backside where it is dificult to see. Replacement is on the way.

    I will check valves. If they need adjustment I will tackle the method.

    Thanks:clap

    Eric
    #7
  8. Tripletreat

    Tripletreat Been here awhile

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    If you can blow the shim out with air pressure, how does one insert the replacement?
    #8
  9. bmwrench

    bmwrench Long timer

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    I may have led you astray; you do need the tool that opens the valve slightly, as well as the tool that holds it open. Once the valve bucket is pushed away from the camshaft, you can pop the shim out with air. BMW supplied a bent set of needle-nose pliers to R&R shims, which didn't work very well. The replacement shim slips in, then the other tools are removed.
    #9
  10. ericrat

    ericrat Long timer

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    Breather hose received and installed, no more hot stalls.:clap

    Thanks everyone!

    Eric
    #10