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Thread: /5 electrical issue/starter button

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  1. #1
    BeemerBoy terham's Avatar
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    /5 electrical issue/starter button

    This being August and all, I thought I'd appeal to this august group with an issue I'm having on my 1971 R75/5.

    Over the last 6 months or so, my starter didn't always engage when I pressed the starter button, but by being more deliberate or pushing the button in a slightly different position, could start the bike. Now even this doesn't work so I figured a little cleaning was in order. I removed the two screws holding the switch to the handlebar, and pulled the switch away from the housing just far enough to visually inspect the wires - no obvious broken wires - and I sprayed some contact cleaner and compressed air around the wires. I still had nothing when the starter button was depressed, so I put it back together, kick started the bike and went for a ride. About an hour later I stopped for gas and thought the idiot lights looked a little dim and the turn signals didn't blink steadily. On the way home the bike sputtered a few times and eventually quit on me. I somehow got the bike restarted and made it home and noticed a weak headlight - I had turned it off for the ride home suspecting an electrical issue, and no tail or brake light. A voltmeter showed a dead battery. I charged the battery overnight - voltmeter read 12.4 or thereabouts, and I went for a ride closer to home and had the same issue - within 30 minutes or so, the headlight was dimmer and the blinkers didn't blink.

    Believing in the "what did you do last?" theory of troubleshooting, is it possible that the issue is related to something I did when I removed the starter button? When the starter button worked intermittently, I did not have this problem. I'm a pretty novice mechanic, especially when it comes to electrical issues, but wonder how to proceed. I figure I should replace the switch, but would like to know how to proceed so I can go farther than an hour from home until I replace the switch.

    Thanks.
    Terence
    R75/5 R100RS K100RS R1100S

  2. #2
    Administrator 20774's Avatar
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    Snowbum has instructions for troubleshooting the starter circuit. That might have pointed you to the issue whether it was the switch, starter relay, solenoid, or even the starter.

    The switch is used to send low current to the starter relay. The relay contacts close which sends lots of current to the solenoid. Once the solenoid engages, the starter turns.

    It's possible that the fluid in the starter switch has bridged a circuit, causing a constant drain on the battery. But you would think you should still be getting a decent charge. What do the battery terminals read when the engine is running above 3K RPM? If not more than 13.5v, then you more than likely have a charging problem...how that is connected to the switch I don't know. Unless the problem with the switch causes such a drain to negate any charging you might be getting.

    I haven't done it, but I think you can put an ammeter connected between the negative ground and the tranny and see if you have any current flow...that would indicate a drain of some kind.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    BeemerBoy terham's Avatar
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    I assume any fluid in the switch should've evaporated? At slightly over 3000 rpm, I'm getting more than15v.
    Terence
    R75/5 R100RS K100RS R1100S

  4. #4
    Administrator 20774's Avatar
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    IF "any fluid" is WD40, it won't evaporate...it leaves behind a gummy surface which attracts dirt/grime.

    You should never see more than 14-14.2v. Sounds like your regulator is not regulating...battery could be cooked along with other wiring.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    Registered User ebeeby's Avatar
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    IF you do not have a load tester, you cannot eliminate the battery as the problem.

    My rule - at the age of 54 - is when troubleshooting an electrical problem on a Motorcycle, step one is to throw the battery in the Mississippi River.

  6. #6
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    I vote for the battery also.

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