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Thread: K75S Battery Fryer

  1. #1
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    K75S Battery Fryer

    I recently purchased an '87 K75S (First Litter, #150086) from an estate sale thru a BMW dealer. It isn't running and I was told that the technician thought the starter was dead, because of a huge amp draw when trying to start the engine. I thought, "no big deal, just get it home and change the starter.". Yeah, right. Being a cheapskate and not wanting to sink a lot of cash into the bike before knowing exactly what I had, I got a used starter on eBay. Got it installed and here's what happened:

    I hooked up the battery, which had been on the charger and was ready to go. I turned on the key and had lights, nice and bright until I hit the starter button. Then, nothing. Absolutely nothing! Lights died and all was quiet, like I had turned off the key. The starter hadn't budged or made a sound. Then, I noticed smoke from the battery, starting slowly, out the vent hose, then a LOT, coming from what seemed everywhere. And the shop got all smelly, like battery acid. I knew this wasn't good, so I flung open the overhead door and turned on the floor fan to get things cleared out. I wasn't crazy about going near a violently smoking battery, but I knew I had to stop the smoking. I finally got the negative cable removed and quickly went outside for some fresh air. When I saw no more smoke emanating from the battery, I courageously went back inside.

    So, now she sits, alone, quiet and lonely. I really want to get her started and hear her run, but I'm unsure how to resolve whatever issue(s) may be causing the problem(s).

    Thoughts, anyone? All constructive advice and suggestions are welcome. Thanks, in advance. Oh, yeah: HAPPY NEW YEAR!

  2. #2
    3 Red Bricks
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    Welcome to the Forum and the MOA!

    Your bike was about 25 feet behind mine (150081) on the assembly line May 16, 1986!

    It would appear that something is shorted in the wiring on your bike.

    The first thing that I would do remove the gas tank (and plug the hoses). Most of the wiring is directly underneath the tank. You don't want fuel anywhere around while you are looking for an electrical short. You will also have good access to all the wiring and relays.

    Secondly, I would remove the battery and place it on the floor with a couple of heavy wires connected and insulated to the bikes cables and at least one (if not both) wires connected to the battery with clips or a switch so that you can rapidly disconnect the battery if things are not going right.

    Check the starter cable with an ohm meter to see if it is shorted to ground. With the starter and battery disconnected, see if the starter cable shorts to ground when the ignition switch is on and the starter button is pressed.

    There are a lot of wires very tightly packed right where they come out of the relay box. There is the possibility that chafeing, a previous owner, or small critters have caused a short.

    One thing to be aware of: trying to crank a Kbike with a low battery will cause the contacts in the starter relay to weld together, constantly energizing the starter. It would be a good idea to have your battery load tested at a local car parts place (usually free) before you start trying to troubleshoot your bike.

    Get back to us with what you find and we'll help guide you to the solution.

    Where in the country are you located?



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
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  3. #3
    Benchwrenching PGlaves's Avatar
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    There is one more thing to do before you go too far.

    On the front of the engine toward the right side of the bike is a small square plate that has two "ears" making it more or less "T" shaped. Remove this cover plate. Behind it you will find a capscrew that takes an 8mm Allen wrench.

    I would remove the spark plugs (behind the black plate on the left side of the engine. Then I would turn the engine using an 8mm Allen socket - clockwise as you face the front of the engine - to make certain the engine turns smoothly. It probably does but I would want to be sure I didn't have a locked-up engine before I spent a great deal of time on wiring.
    Paul Glaves - "Big Bend", Texas U.S.A
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    Thanks for the bike build info, electrical advice and quick response. I'll try the things you mentioned and, of course, post the results.

    I'm in the Salem, Oregon area, a recent retiree transplanted from Sacramento. When my bike can make a trip to the City, we should get our rides together and re-introduce them. At the Marin or San Jose shop, perhaps? Thanks, again!

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    Thanks, Paul. You apparently posted as I was writing my response to Lee's post. Great idea, I'll definitely do that first. Thanks!

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    Registered User dieselyoda's Avatar
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    All of those and one odd one to add.

    Any of the advice you have so far could be deadly accurate. When I first read your post, my gut instinct was shorted plates in the battery. That can be uber major dangerous. Fire is easy enough to manage, explosions tend to be more problematic and that can/does happen with shorted batteries.

    If it was my problem, I would disconnect the NEGATIVE cable, put a test light in parallel, and hit the starter button. Two things could happen, the light doesn't change or the light gets bright. If the light gets bright, ignore my advice and follow the previous comments. If nothing happens, battery be da bitch.

    For those unfamiliar with dealing with frozen batteries, we were as cold as Mars this week, stuff happens to batteries and it can be a guess but more importantly, really dangerous.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case)
    1986 K75S(the beutch), 1993 K1100RS (blown engine), 1997 Chev Short Box (4x4 with an LT1)
    "You can easily judge the character of a man by how he treats those who can do nothing for him."

  7. #7
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    Given that a half charged battery can freeze in the teens (F) IIRC, certainly possible- though its a whole lot more difficult to freeze a fully charged one. Even dilute sulfuric acid isn't pretty if one manages to blow the case apart..

    Takes a serious current dump to fry a batt that way- that kind of current is full starter draw or more, not a short of some little wire. If the motor turns the short ought to be easy to find if its not that batt- probably burned something else too.

  8. #8
    Still plays with trains. tinytrains's Avatar
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    It seems to me, if the short was big enough to make smoke come out of the battery, there should be melted plastic on the cables that would be easy to see. The starter cables should have been red hot if shorted that long. It sounds like a bad battery to me that shorted internally.

    I would remove the battery from the bike and measure the voltage. If it does not show any voltage, it is probably internally shorted.
    If it reads 12 volts or more, put a charger on it (out doors of course!) and see what it does.

    While the battery is out, measure the resistance between the battery cables. With the key off, it should be near infinity. If the starter (or anything else) is shorted, it will be zero.

    Paul has a good point about checking that the engine is not frozen too. If you put the bike in 5th gear and push (key off), the wheel should turn and the engine spin. If the wheel slides, it may be frozen.
    1988 K75 Low Seat
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  9. #9
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    Alternatively, in addition to the above, disconnect the alternator and see if that is the issue. I have seen major drains on batteries because one of the diodes in the alternator went bust and created a 2.5 Amp drain even without the bike's contact on.
    The effect you have seems a full drain to ground/earth - starter motor bushes gone completely?
    Let us know more.

    Regards, Rene

  10. #10
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    OK, folks, quick update. I haven't had much time to work on the bike, but here's what I also know now: Battery out of the bike, just sitting since frying, it shows 12.3 volts. Strange. The motor turns by way of the crankshaft allen screw, but very easily, like there's no compression, rather than being frozen. Stranger. Also, when The Fry happened, it was cold, but above freezing and has been about the same since. I haven't done much else, other than removing the bodywork so I can reach everything more easily. Hoping to get a chance to work on her today, so I'll keep you posted.

    Thanks, again, for the advice and suggestions.
    "When you don't know where you're going, any road'll get you there"
    -George Harrison

  11. #11
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by Dustpan View Post
    The motor turns by way of the crankshaft allen screw, but very easily, like there's no compression, rather than being frozen.
    With the plugs out those engines do turn easily.

    Another thought based on an experience on an R1100 on which the starter wire had shorted directly to ground. Carefully examine specifically the wire between the starter relay in the box under the rear of the tqank and the lug on the starter. If this wire is shorted to ground you would get exactly the symptoms described.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  12. #12
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    Unhappy

    But, I failed to mention?The plugs were still in.
    Last edited by Dustpan; 01-05-2014 at 04:20 PM. Reason: mistake
    "When you don't know where you're going, any road'll get you there"
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  13. #13
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    Another brief update. Unfortunately, I'm now more confused than ever. With the battery removed, alternator unplugged and my trusty old analog VOM in hand, here's what I've found:
    1. Continuity (full 90 degree needle swing) from one end of negative cable to the other end. Good, expected.
    2. Continuity from one end of Positive cable to the other end of the cable. Again, good and expected.
    3. Partial (about 80 degrees needle swing) from one end of neg cable to one end of pos cable. Not expected and not good.
    4. Partial (again, 80 degree swing) from alternator pos terminal to ground. Not good.
    5. Continuity from starter cable terminal to ground. The original starter that I removed also has continuity from the post to the case, which shouldn't be happening. So, I'm assuming my, "new" used starter is bad, as well. Or, the old one was OK and not the cause of the problem.

    I know there must be a short or some connection, somewhere, that's bad, but I'm damned if I can find it. All the visible portions of the wiring look good (no chafing, melted insulation, etc.), so I'm wondering if maybe the problem is in a relay, or some other component.

    All I'm sure of, at this point, is that I'm not hooking up my new $160 Ballistic battery until it's fixed! Thanks, all.
    "When you don't know where you're going, any road'll get you there"
    -George Harrison

  14. #14
    Registered User dieselyoda's Avatar
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    Wow man, I think you are thinking too hard.

    You will get continuity from between the positive and negative cables with anything with Keep Alive Memory, like your clock or ECM. Positive on the alternator is the same as the positive on the battery. Current draw is the most important here and if it lights up a cheap test light real bright, you have an issue.

    The starter thing has me baffled. Two in a row bad? I doubt that so I wonder what you are testing. Big post to ground should not have continuity. Solenoid/relay post to ground needs continuity to the tune of about ten ohms. The reverse occurs if your solenoid is ground switched through a controller. Regardless, positive big post to ground/case, should be no continuity.

    Remember, continuity and resistance are two separate things. You can have proper resistance in a circuit and continuity.

    There is continuity through the alternator to the tune of lots of mega ohms and that would make resistance very high but carries no current.

    If we are still talking the original problem you described: buy a handful of those little square nine volt batteries. Buy a Boy Scout compass or lots of boxes of Cracker Jacks until you get a cheap, simple compass. Hook up the battery to the bikes cables. when the battery gets hot, scan the bike with the compass. The "N" pole will point you directly at the short.

    When you cook that battery and still can't find it, try again.

    If you want, jumper cables from a good set of wheels and look at the spark when you connect the last cable. If the spark makes you want to pee yourself, you have a problem. If the spark is weak, you probably are dealing with a minor problem that will be exceedingly hard to find.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case)
    1986 K75S(the beutch), 1993 K1100RS (blown engine), 1997 Chev Short Box (4x4 with an LT1)
    "You can easily judge the character of a man by how he treats those who can do nothing for him."

  15. #15
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    OK, score , "1" for dieselyoda! Finally got some time to play with the bike and have made a couple discoveries. First, the old battery showed 12.something volts, so I put it outside with the charger on it. Waited a couple hours, no smoke, no hot, no anything detrimental. So, I took it back inside and hooked up a small 12v LED I had lying around and....nothing. Still showed 12.something volts, but had zero amps. So, I quickly deduced the battery is gone. Then, assuming the problem was an internal short, I put the new battery in the bike and hooked up the positive cable. I then wired a quick-disconnect into the negative cable and turned it on. Nothing happened. This is good! Turned the key to the, "Park" position and the tail light and park light came on! This, too, is good. Then, I turned the key to, "Run" and the head light came on. Still no smoke or other bad things. Awesome! Then, holding my breath, I hit the Start Button. The engine started cranking, no smoke, no bad stuff. Until I released the Start Button and the starter and engine continued cranking. I hit the Kill Switch. Nothing. Still cranking. So, I quickly undid the rigged-up quick-disconnect. Of course, everything stopped. I waited a minute, then connected the quick-disconnect. The starter and engine immediately started cranking, again. I undid the quick-disconnect and decided I have a bad starter relay. Someone previously tried to start it with a low (shorted-plates) battery and welded the contacts together, is my guess. So, I guess I'm done until the replacement relay gets here, unless someone has a better idea?

    Again, thanks for the help.
    "When you don't know where you're going, any road'll get you there"
    -George Harrison

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