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Thread: /5 electrical issue/starter button

  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.

  7. #7
    Registered User lmo1131's Avatar
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    I vote for the battery also.
    Having gone through a charging system problem this summer, my new mantra is, "if the charging system is performing poorly, suspect the battery first.

    Weak turn signal flash rate while under power = not getting enough juice to drive the flasher relay.

    Sputtered and died = no charge on the battery.

    The alternator requires 13+ volts from the battery to energize the field (help me out with terms here guys)... if it doesn't get it it doesn't put out, ... it's a vicious circle.

    Read the link I posted above.

    Just for giggles, how old is the battery?
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  8. #8
    BeemerBoy terham's Avatar
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    Thanks for the link Lew, I'll give it a read more thoroughly tonight. I checked my records, and if they're correct, this battery is from 2007 - I didn't realize it had been that long. Thanks for asking that question. I have a battery I can use and will put it in and go for a ride this weekend and see what happens.
    Terence
    R75/5 R100RS K100RS R1100S

  9. #9
    James.A
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    A 5 year old battery should be retired as a matter of course. But, 30 minutes of running time before the battery goes flat could also be a charging problem. Here's a trick you could try. Charge up the battery, then pull the blue wire from the bottom of the starter relay. If the starter engages, you have an open rotor in the alternator.

    There is an analog logic circuit in the starter relay. It is part of the anti-restart function on /5's only. The starter relay dis-engages the starter circuit when the motor is turning. The relay identifies the motor as running by looking for alternator current output and when that is present the starter will not engage. When the alternator rotor goes open, the relay defaults to the no start condition. Pulling the blue wire defeats the anti-restart function entirely.

  10. #10
    Bluenoser
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    I also suspect the battery. Resting voltage of 12.4 is too low and its probably about 50 % charged at that rate. If you get 5 yrs out of a standard wet cell in a motorcycle you are doing well.

    I would replace the battery before I did any of the other checks. Unless you have a fully charged battery to work with the other checks are bordering on a waste of time. Make sure you charge up the new battery before you use it. If you can put it on a low voltage charger 1.5 amp or less for 24 hrs it will really help in the lifespan of the new battery.
    1971 R50/5 SWB with R75/6 drivetrain
    2013 DL650

  11. #11
    BeemerBoy terham's Avatar
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    Here's an update - I've been working on this problem off and on, but can't believe it's been 3 months already.

    I first replaced the battery with a new one and using Rick Jones' manual, traced the charging problem to the rotor, though I haven't replaced the rotor yet.

    I still have the problem with the nonfunctioning starter and it's driving me crazy. Here's a summary of what I've done. If I disconnect the black wire that runs from the starter relay (terminal 87) to the starter, and jump this black wire, the starter turns over. If I disconnect the brown/black wire that runs from the starter button into the starter relay (terminal 31b), and jump the male connection, the starter turns over. Seems to me the starter is good and the relay is good - I replaced the relay anyway and that didn't solve the problem.

    With the ignition off, if I put the positive lead of my meter on the positive battery post and put the negative lead into the spade connector on the disconnected brown/black wire from the starter button that connects into the starter relay, I read 0v and when I press the starter button I get 12v. I assume this means the starter button is OK?

    If I disconnect the blue wire from the relay, I still have the same problem.

    I had an extra voltage regulator around and putting the new one in had no effect.

    In my feeble attempts to fix this problem, it seems to me the starter button is OK, the relay is OK and the starter is OK. What am I overlooking?
    Terence
    R75/5 R100RS K100RS R1100S

  12. #12
    Registered User
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    "With the ignition off, if I put the positive lead of my meter on the positive battery post and put the negative lead into the spade connector on the disconnected brown/black wire from the starter button that connects into the starter relay, I read 0v and when I press the starter button I get 12v. I assume this means the starter button is OK?"

    MAYBE NOT - RETRY THIS TEST WITH SOME LOAD LIKE A BRAKE LIGHT IN SERIES INSTEAD OF METER

    "I sprayed some contact cleaner and compressed air around the wires."

    CLEANER AROUND WIRES MAYBE NOT CLEANER ON THE SWITCH CONTACT SURFACES

  13. #13
    Monza Blue 1974 R90/6
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    I was fooled by a meter on a problem like this. I was getting 12+ volts on my digital meter, so thought all was ok. Turned out to be a mostly broken wire in the harness. There was enough of a connection that the meter could see the 12 volts, but the wire couldn't pass any real load. Same situation can happen with a corroded or loose connector.

    That is why the above recommendation to use a lamp as a load tester is good.

    Barron

  14. #14
    BeemerBoy terham's Avatar
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    If I interpret what you're saying correctly, I attached a test lamp to the spade connector on the black/brown wire from the starter button and the other end to the positive battery post. With the ignition off, the test lamp is off and when I press the starter button, the lamp comes on. I turned on the ignition and pulled the front brake lever - brake light is on and test lamp is off - and when I press the starter button, the test lamp comes on.

    I visually inspected each of the connections at the starter relay, the starter, inside the headlight shell and best I could inside the starter button, and don't see any broken wires or corroded connections and the connections are tight i.e. I can't pull the connections without wiggling the wires a bit. If the problem is an individual wire inside a harness that I can't see, I'm not sure how to trouble shoot this?
    Terence
    R75/5 R100RS K100RS R1100S

  15. #15
    R100GS, '89 Guenther's Avatar
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    You could follow the signal from one-end to the other and find where it stopped.

    With all wires connected connect the voltmeter "+" to the spade of the br/bk wire from the starter switch at the point where it connects to the starter relay and the voltmeter "-" to ground. If the volts drop from 12V to 0V when you push the starte button then this section seems to be ok.

    Next do the same test for the black wire that goes to the starter. First check at the point where the wire is conencted to the starter relay and then the other end where it connects to the starter solenoid.

    I would be dam'ed if you don't find the spot where it fails.

    /Guenther

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