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Thread: 1990 K75 RT troubles

  1. #1
    Nick Kennedy
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    Nov 2011
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    Telluride Colorado
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    1990 K75 RT troubles

    1990 K75 RT
    Battery 28 months old, kept on tender.
    So last Sat Am I go to start my K 75. The ign. key seems really stiff, bound up really and takes a few tries to get it to turn on.
    I go to start it and it seems the battery is really low, almost dead, I jump it off my van and take off.
    1/2 hr later I stop for gas and it wont restart and the starter relay sticks on.
    I disconnect the ground lead and reach in with a screwdriver and tap the starter relay and get it to open.
    I bump start the bike and head home early.
    I get home and put a VM meter across the battery and go for a spin. 13.4-5 v. I let it sit and battery stabilizes at 12.8v
    Key is still stiff but it turns and bike starts fine.
    Battery seems good to me.
    I pull my ign switch and clean it yesterday and it works much better now. For those in the know, could a gummed up ign switch cause this seemingly low battery condition?
    Battery has sat for 48 hrs now and reads 12.7 v.
    Thanks in advance
    Nick
    Ps I'm getting good at pulling that switch out now and cleaning it, whole procedure was performed in 40 mins.

  2. #2
    Registered User GTRider's Avatar
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    Connect a voltmeter across the battery and take a reading while cranking the starter. If it drops below 12v while cranking its suspect. Or, you can take the battery to an auto parts store like Autozone and have it load-tested. If the battery checks ok the next thing Id try would be to clean and de-oxidize all the connections between battery, relay, and starter as well as checking and cleaning all the ground connections.

    Sticking of the relay contacts is usually caused by low cranking voltage, usually a bad battery or connections. I cant speak to the switch as Ive not seen one cause the situation you describe, but removing and cleaning the switch certainly cleared/cleaned the contacts.

    Best,
    DeVern
    DGerber
    1983 R80ST 1984 R80 G/S-PD 2004 K1200GT w/Hannigan S/C 2010 K1300GT 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

  3. #3
    3 Red Bricks
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    Quote Originally Posted by nickrides View Post
    For those in the know, could a gummed up ign switch cause this seemingly low battery condition?
    Nick,

    Absolutely.

    Take your voltmeter and put one probe on the back of #1 fuse (There are two holes on the back of each fuse. Either hole will do for this test.). Put the other probe at the ground bolt on the side of the transmission above the shift lever.

    Turn on key and kill switch to run. Voltage should be within .5 volts of battery standing voltage across the battery terminals with key off.




    Last edited by 98lee; 11-03-2020 at 07:32 PM. Reason: Added kill switch position
    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  4. #4
    Nick Kennedy
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    Nov 2011
    Location
    Telluride Colorado
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    DeVern
    Its hard to get a battery cranking voltage as my bike starts so fast.
    It seems I touch the starter and it lights right off.
    But I'll clean the grounds and see what I find.
    The nearest Place with a load tester is 80 miles away, but the next time I go down there I'll bring this battery with me.
    Best
    Nick

  5. #5
    Nick Kennedy
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    Let me run some tests after work today and I'll report back what I find out.
    Thank you
    Nick

  6. #6
    Nick Kennedy
    Join Date
    Nov 2011
    Location
    Telluride Colorado
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    Final Report
    It was the Battery, a 28 month old SLA called a Mighty Max.
    Don't buy one of those!
    I looked in my Maint. log and saw my old Walmart battery, a Ever Start, lead acid battery before this one went 7 years, never fully died, just got a bit weak.
    So I bought another one, 60 bucks.
    All better now.
    Funny how the Ign. switch got very hard to turn at the same time, opened it up, cleaned it, but it was clean to start with.
    Bike is stored in a heated garage.
    Oh well- its 30+ years old now, I still like to ride it!
    Nick
    1990 K75 RT

  7. #7
    Registered User GTRider's Avatar
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    Glad you resolved the issue; enjoy the ride!

    DeVern
    DGerber
    1983 R80ST 1984 R80 G/S-PD 2004 K1200GT w/Hannigan S/C 2010 K1300GT 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

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