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Thread: K75 starting problen

  1. #1
    S Forstner
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    Question K75 starting problen

    I have a friend's K75 in my garage for a little TLC. The bike was put up two years ago due to unspecified poor running problems. What I find now is that it is very difficult to start. It misfires and locks up at random when trying to start it when cold. With some patience it can be coaxed to start. It will run very rough until fully warmed up when it will purr like a kitten. When warmed up it will restart with no problem and when let to idle it will engage the radiator fan so I know the coolant sensor is working. My only guess is that the computer has locked the ignition curve in to running at full advance. Is my guess correct? Is there something beside the coolant temperature that will affect the timing advance? Any help will be appreciated. Any guesses out there?

  2. #2
    3 Red Bricks
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    Try new spark plugs.


    LONG MAY YOUR BRICK FLY!

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    Lee Fulton Forum Moderator
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  3. #3
    Benchwrenching PGlaves's Avatar
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    I seriously doubt this is a computer (LJetronic) issue. I suspect a faulty temperature sensor. I also suspect some partially clogged/dirty/gummy fuel injectors.
    Paul Glaves - "Big Bend", Texas U.S.A
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  4. #4
    S Forstner
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    Quote Originally Posted by PGlaves View Post
    I seriously doubt this is a computer (LJetronic) issue. I suspect a faulty temperature sensor. I also suspect some partially clogged/dirty/gummy fuel injectors.
    Thanks Paul, I suspected the temperature sensor but had dismissed it as the cooling fan engaged after the bike warmed up. Guess I will pull it and put it into boiling water to see if it croaks. The plugs were replaced and the gas replaced with E-0 with Startron additive to give the injectors a chance. Past that would the Mass air flow sensor or the O2 sensor cause this type of symptom?

  5. #5
    3 Red Bricks
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    There is no O2 sensor on a K75.


    http://ibmwr.org/ktech/cold-run-problems.shtml



    LONG MAY YOUR BRICK FLY!

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    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
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  6. #6
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    You likely have something else going on, but this may help as well - consider changing the oil to something lighter, and when you start the bike, sit on it and hold the clutch in.

    Two winters ago I was having some reluctant cold-weather starts, and on a lark when it was time for an oil change, I swapped out the 20w50 for Mobil1 0w40 to see if a significantly lighter oil would provide noticeably less resistance. You know what? I think it did.

    I was also in the habit of starting the bike on the side stand before climbing onto it, and letting it warm up while I fussed around with helmet/gloves/whatever. Even in neutral, this requires the starter to crank against the inertia of the transmission and the thick gear oil. Holding the clutch in noticeably improved my cold-weather starts. This doesn't work with a properly functioning side stand, of course.

    Did you change the fuel filter, BTW? Have you pulled out the fuel pump to check the condition of the rubber damper around it?

  7. #7
    S Forstner
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    Been a few days but this really seems to be an electrical problem. After putting everything back together from my examination of the coolant sensor, I tried to start it again. Seemed to want to start then started acting up: starter kicking out and trying to reengage. Then the starter engaged and wouldn't stop even when the ignition was switched off . Pulled the positive battery lead (convenient on the standard K75) to stop the unwanted activity. Looks like I have a relay or starter issue that is sending me up the wall . The battery should be fully charged but it is going back on the Battery Tender tonight. We'll see what tomorrow brings.

  8. #8
    Benchwrenching PGlaves's Avatar
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    The starter staying on is a stuck starter relay. They usually stick when a start is attempted with a very weak battery. I think the battery is bad. You will also need to deal with the stuck starter relay. Sometimes a sharp rap with a screwdriver handle will jar it loose. It is in the right rear corner of the electrics box under the rear of the fuel tank - the one with the big wires bolted to it. I personally prefer to replace them, but lots of folks have had good luck even longer term after rapping to break the contacts loose.
    Paul Glaves - "Big Bend", Texas U.S.A
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  9. #9
    S Forstner
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    OK, so it should be the starter relay. Makes sense. So... out a C note for an 'Officaial" Bosch starter relay and the same thing happens. Put the new relay in and did a short try before replacing the tank and the starter sounded good. Added the tank and hooked up the fuel pump connection then we have instant starter. Once the button was pushed the starter stayed on. You know the drill. What else should I check?

  10. #10
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    Paul's post just above yours explains it.

  11. #11
    A bozo on the bus deilenberger's Avatar
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    I'll just emphasise what Paul said: "They usually stick when a start is attempted with a very weak battery" - the only real test of a battery is a "load" test, where a heavy load is put on the battery and then the voltage is observed, watching to see how long it takes the battery to recover from the heavy load. A battery can read fully charged when looking at voltage alone, but if it's badly sulphated - it will take a surface charge that has very low current reserve, and that can drop the voltage enough to destroy the new $100 starter relay.

    I'd either check the battery at a battery shop that has a load-tester, or if it's more than a few years old or has ever been heavily discharged (and left partly discharged) - replace it with a new one.
    Don Eilenberger http://www.eilenberger.net
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  12. #12
    Registered User 58058D's Avatar
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    Now that you have a NEW battery and two fried starter relays....you can pry (prise in teutonic?) the plastic cap of one and separate the contacts with a small screw driver. Maybe clean it up with a fine emery cloth. Snap it back together and give it another shot, all should be good -BTDT....But Not until you have a NEW battery in there. At least you apparently don't have ABS because that is the other relay that can get fried by the low battery, but frying the starter relay is almost a guarantee when your battery is bad. I was once told: How do you load-test for a bad battery? Try starting and if it fries your starter relay, the battery is bad.....
    Jim Douglas '00 K1200RS >135,000 miles my primary bike again,
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  13. #13
    PeteG
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    Battery voltage test

    Jim (58058D), I know you can test an auto battery using a multimeter with a min/max function by connecting the meter and starting the engine. On an auto battery if the min. voltage goes below 9.6v then your battery needs to be replaced.

    Is this test valid for a motorcycle? Does the 9.6v minimum amount apply? Anyone know.

    Thanks,
    Pete

  14. #14
    Benchwrenching PGlaves's Avatar
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    Just get a new battery. The bike sat for a long time!
    Paul Glaves - "Big Bend", Texas U.S.A
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