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Thread: Can you help me figure out what's wrong?

  1. #1

    1977 R100S: Can you help me figure out what's wrong?

    Ok, I'll probably be using this thread to mention any problems I encounter, instead of cluttering the forums.

    So, I took out the battery to let it charge. It is an AGM battery, and my charger said it was sulfated, so I let it do the repair. It finally started showing signs of taking a charge, but won't charge to 100%. Seeing as this is the first AGM battery I have every had, I wanted to try to save it. Unfortunately, it doesn't have enough power to crank the engine (as you'll see in the video I'm going to link). So I'll have to replace that battery when I get money. I'm worried something in the electrics might have gotten rongled as well, as the engine will only turn when the kill switch is set to "Off." The headlight will also need attention, as the low beam appears to not work, and the high beam will turn on, but will only stay on if I apply pressure to the switch (indicating a bad or corroded contact).

    Last edited by zombiepotatosalad; 11-24-2022 at 03:06 AM. Reason: Forgot to add year and model in title

  2. #2
    Registered User STEVENRANKIN's Avatar
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    Video

    Hello, thanks for sending the video, it is informative.

    Let me start with the battery, if it won't charge to 100% in a reasonable time, ditch it, it is dead. Sorry to be blunt.

    As for the bike not starting with the kill switch on, makes me believe the kill switch is wired or connected in the headlight shell improperly. Also, when the ignition key is on, there should also be the oil pressure light on as well as the generator light, not just the neutral light. The oil pressure light should go out a second after fast cranking the bike and pressure is built up. The generator light will go out IF the charging system is working properly at 2000+ RPM.

    So, what I would do is open the headlight shell, and check the wiring. IF everything is factory wired, each wire coming into the shell will plug into a circuit board at the same color location as the wire. You can take a quick glance and see if something is obviously not plugged into the proper colored spot. If you can't spot something obvious it is time to get a wiring diagram and trace things out.

    If this bike has been rewired by a previous owner, it is any guess as to what is up. At that point only a good wiring diagram and patience will help along with a test light and voltage meter.

    Good luck and if you can post videos like you did with any progress or updates. Good luck, St.

  3. #3
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Iím used to basic lead-acid battery charging and really have to think about which charger/charger methods once I get past basic batteries. I usually factor in battery age if there seems to be a problem.

    Brook has some great wiring information in the link in this thread that may help-

    https://forums.bmwmoa.org/showthread...urce-Materials

    Good luck.

    OM
    "You can do good or you can do well. Sooner or later they make you choose." MI5
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  4. #4
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by zombiepotatosalad View Post
    Ok, I'll probably be using this thread to mention any problems I encounter, instead of cluttering the forums.

    So, I took out the battery to let it charge. It is an AGM battery, and my charger said it was sulfated, so I let it do the repair. It finally started showing signs of taking a charge, but won't charge to 100%. Seeing as this is the first AGM battery I have every had, I wanted to try to save it. Unfortunately, it doesn't have enough power to crank the engine (as you'll see in the video I'm going to link). So I'll have to replace that battery when I get money. I'm worried something in the electrics might have gotten rongled as well, as the engine will only turn when the kill switch is set to "Off." The headlight will also need attention, as the low beam appears to not work, and the high beam will turn on, but will only stay on if I apply pressure to the switch (indicating a bad or corroded contact).

    Saving a sulfated battery is an iffy proposition, however I have had excellent results using the "Repair" mode on the NOCO Genius series of chargers like this Genius5 https://www.amazon.com/NOCO-GENIUS5-...ef_=ast_sto_dp. I use Odyssey AGM batteries exclusively and have gotten 8 to 11+ year from them. One such battery started not taking or holding a full charge as it should so I ran it through the Repair mode several times (NOCO says you can do that multiple times) and that was in the summer of 2020 and I'm still using it.

    Besides that, I think others here have identified that you have some wiring issues which must be sorted. Be careful as airhead wiring harnesses are not overly blessed with fuses.
    Greg Feeler
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    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  5. #5
    Registered User STEVENRANKIN's Avatar
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    Odyssey

    LOL, since having switched to Odyssey several years ago, I haven't had a failure due to battery. If I do, I will try out the advice given here. A shameless plug for them, they are worth the money. St.

  6. #6
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by STEVENRANKIN View Post
    LOL, since having switched to Odyssey several years ago, I haven't had a failure due to battery. If I do, I will try out the advice given here. A shameless plug for them, they are worth the money. St.
    I'll add that my experience with Odyssey batteries is with four K-bike in concurrent use. If most things were this good...
    Greg Feeler
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  7. #7
    Registered User ebeeby's Avatar
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    +1 on Odyssey batteries.
    1973 R75/5
    1975 R90S

  8. #8
    Curmudgeon nrpetersen's Avatar
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    +2 on Odyssey. I've had 2 bikes w Odyssey PC680's, now down to one. One battery I replaced on general too-old principles but it is still live after what has to now be 15 years. Battery Tenders (the 750 ma series) kept all of them up.

    It is important to use only a charger system that totally cuts off at a certain voltage. Continuing to trickle charge for a long time will still kill a battery. I use a pulse type chargers for a week or two when trying to recover any sulfated battery.
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

  9. #9
    #13338 PGlaves's Avatar
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    For many years before "smart" chargers became affordable, Voni and I had a fleet of motorcycles. At the peak we had 9 licensed and insured bikes. I had one "dumb" 2 amp charger. During the winter in Kansas we might take a short ride each month but for the most part the fleet remained parked in the cold months.

    So I had a routine. On the first day of each month I would charge one bike's battery for 24 hours. Move to the next bike the next day, for 24 hours. I would continue this routine until all of the bikes had been hooked to the charger for 24 hours.

    This routine worked well 20 years ago because all of those bikes had very low, if any parasitic battery drain. The clocks on the K75s were probably the highest drain but charging for 24 hours once a month still worked just fine.
    Paul Glaves - "Big Bend", Texas U.S.A
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  10. #10
    Registered User STEVENRANKIN's Avatar
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    Old routine

    Yeah, back in the days of lead acid batteries and dumb chargers, I would remove the batteries from the bikes as well as power equipment and rotate charging with a trickle charger.

    Now I have a four bank Battery Tender and it is great to just plug and charge no worries about overcharging. St.

  11. #11
    While the Odyssey brand batteries may be long lasting, they do cost more than a regular battery, about $240 on eBay. I just bought another Chrome brand AGM battery for the airhead, about $85 on eBay. I maintain batteries on a tender and replace them about every 5 years just to be safe, so if an Odyssey will last 15 years the total cost works out about the same.
    -Live as fully as you can as long as you can-

  12. #12
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    Can you help me figure out what's wrong.

    Quote Originally Posted by OldCamper View Post
    While the Odyssey brand batteries may be long lasting, they do cost more than a regular battery, about $240 on eBay. I just bought another Chrome brand AGM battery for the airhead, about $85 on eBay. I maintain batteries on a tender and replace them about every 5 years just to be safe, so if an Odyssey will last 15 years the total cost works out about the same.
    $240 for a PC680?????
    How about this....$135!!!!!
    https://www.amazon.com/ODYSSEY-PC680...002ILK6I&psc=1

    Since I started using Odyssey batteries I have never been disappointed by them. I leave them on a Battery Tender when not in use. The desert is an extreme environment for batteries, but I've had the Odysseys in bikes for 7-8 years. A wet battery would be waving the white flag at 2-3 years.
    Just an old guy here. Killin' bugs at a rapid pace since '68. Desert dweller.
    Current force: '77 R100/7 ,'85 K100RS-Aug84, '85K100RS-Aug84, '85 K100RS-June85, '93K1100LTSE, '93 K75LTP, '98 R1100GS, '08K1200GT, (2)'72 CB 750s, '76 Honda CB500,

  13. #13
    Quote Originally Posted by Danl View Post
    $240 for a PC680?????
    How about this....$135!!!!!
    https://www.amazon.com/ODYSSEY-PC680...002ILK6I&psc=1

    Since I started using Odyssey batteries I have never been disappointed by them. I leave them on a Battery Tender when not in use. The desert is an extreme environment for batteries, but I've had the Odysseys in bikes for 7-8 years. A wet battery would be waving the white flag at 2-3 years.
    This is the eBay link I referenced.

    https://www.ebay.com/itm/16564561494...Bk9SR6yaiPqWYQ

    Your link is much cheaper.!
    For $135 I may try one myself.
    Thanks!
    -Live as fully as you can as long as you can-

  14. #14
    The battery isn't the problem, I already ordered a battery that will serve for now. The issue is the wiring. I don't know why the kill switch is wired backwards, or how exactly to fix it. The GEN light did come on briefly last night, so I know it works (it seems to be a dirty connection).I got the headlight bucket open, and I can see the wire board. For some reason, the picture is sideways. The left side is the top.

    20221126_220749.jpg

  15. #15
    Registered User STEVENRANKIN's Avatar
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    A quick look

    A quick look shows me one possible spot for your trouble. From left to right you have a bundle of wires in a taped bundle. This is not factory. Can you trace the bundle back outside the shell to the right controls? I don't know what the previous owner did but I guess the black wire (I don't have my schematic handy so I am relying on memory) is possibly the kill switch wire. Regardless, wires from the factory if they have ninety degree plug ends on them inside the headlight shell will plug onto the same color terminal on the circuit board. I see a white (what looks like a factory plug) plugged into a black crimped on connector with tape over it. Same with a yellow wire going to green.

    If you get my drift, this is not correct. Do you have a wiring diagram for the bike, at this point you will need one to figure out what the previous owner was trying to accomplish.

    I always stress keeping stock wiring stock, and in a case like this if possible reverting back to stock.

    If I get out to my shop tomorrow, I will try to see if I can find what goes where.

    All the terminals plugging into the circuit board should be the same color wire as the circuit board. Maybe the previous owner replaced the stock right hand switch control with one that had a shorter wire bundle and added a non correct color group of wires to bridge the length distance. If so, he may well have mis wired somewhere.

    Good luck and good hunting. St.

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