1995 R100RT Classic - Sudden engine cutoff

Discussion in 'Airheads' started by Muravey, Aug 14, 2019.

  1. motu

    motu Loose Pre Unit

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    Alternator ripple ? The AC waveform is still present after rectification, too much and it can interfere with other sensors. This is a test some meters give. Many years ago I had a Subaru in with random faults, and Alt ripple was very high, I took a risk and replaced the alt, and it was all good. Calling Warin again on that one....
    #41
  2. durtwurm

    durtwurm Talented Amateur

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    I am now watching this thread. Wish you well in your search for a fix. And the story continues.....
    #42
  3. ccmickelson

    ccmickelson MonoMania Supporter

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    So in that case would the problem not stem from a faulty diode board on an airhead? He could determine how much, if any, AC is present by putting a multimeter set on low AC on the battery terminals or maybe better the output of the diode board?
    #43
  4. boxerboy81

    boxerboy81 Stay Horizontal

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    I've added the video to an airheads fb page. No solution from there yet.

    Re the kill switch..Snowbum replied
    "Unlikely. When the GEN lamp extinguishes, that also corresponds, well, normally, to an increase in system voltage, ...which is more likely to make something work, rather than not! "

    He also mentions "Can be several things, including battery connections, starter relay connections, corrosion at that relay (which jumpers the electrical system). I'd be using a voltmeter and find out where the power stops."
    #44
  5. Beemerboff

    Beemerboff Long timer

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    Had a similar problem, was bad contacts in the ignition switch.
    Clue here might be wear on the console where a fob an the key was flapping around in the wind, and and also jiggling the contacts.
    Some switches have a spare accessory connector which might be able to be used, or you might be to bypass the switch contacts by hot wiring to the feed to the stop light switch.
    #45
  6. ME 109

    ME 109 Long timer

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    This interference issue hasn’t been mentioned before with oe beancan components, not that I’ve read about anyway?
    #46
  7. bmwrench

    bmwrench Long timer

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    I'd temporarily disable the alternator by unplugging the DF terminal. I'm wondering about the condition of the 3-pin terminal from bean can to engine harness.
    #47
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  8. Warin

    Warin Retired

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    The signal from the bean can is ~10 volts peak to peak. That is the only electronic sensor the airhead has.
    On a suby you have knock sensors ... 1 to 2 volts.. temperature sensors 0.1 volts etc etc ..
    Interference has a much better possibility on a suby than an airhead due to the signal size and the number of signals.. I'd think your bad alt might have a bad diode board.. :1drink

    ---------------------
    The bike will run on a fully charged battery for many miles (no headlights etc, just the normal stop lights, indicators). Easy test as per bmwrench above.
    #48
  9. motu

    motu Loose Pre Unit

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    Yeah, it was the temp sensor getting hit, it was a sizeable ripple, about 4v.
    #49
  10. ME 109

    ME 109 Long timer

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    I don't think the problem is anything to do with the alternator.
    Watching the vid in post 1 makes me think it's a loose connection in the ignition.
    Bike idles well enough, cuts out. Bike revs well enough, cuts out. Both cylinders affected.

    Kill switch tested....but maybe down stream of a fault.
    Starter relay?
    Key ignition switch?
    Clutch switch?
    Bike seems to start and idle each time starter button is pushed.... until it stalls. Same fault as when revving high.

    I dunno.
    #50
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  11. durtwurm

    durtwurm Talented Amateur

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    I have had similar issues and have traced them to an ignition switch problem on more than one occasion.
    #51
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  12. Warin

    Warin Retired

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    Hot wire it ... short from battery positive to ignition coil positive. Would be good to put a switch in the hot wire so you can turn it off. But this would provide an independent source that would prove it is not the standard wiring from battery to coil (fuses, wire, key switch, engine kill switch, connectors).
    #52
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  13. Beemerboff

    Beemerboff Long timer

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    I have had similar symptoms with ignition switch problems too.
    Some suggest that a hot wire to the rear stop switch will back feed the ignition switch, but not as certain as a switched and fused hot wire to the coil.
    #53
  14. Muravey

    Muravey Folk you.

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    IMG_20190907_180751.jpg



    Can't type too well or too much as I'm on a small screen right now, but here is a video I just shot of the bike running fine with the regulator relay disconnected. No other changes to the wiring.
    #54
  15. Muravey

    Muravey Folk you.

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    Mr. Robin Frankham suggested to me via YouTube that I should try to shunt the D+ and DF pins on the regulator relay's connector (with the connector itself disconnected from the regulator) to rule out the regulator from the list of parts potentially at fault:

    As we all know, there is no better time to fiddle with electrical gremlins than in the absolute dead of night (it was midnight an hour ago here), so I skedaddled down to the bike, took the gas tank off, shunted the pins and fired it up. Unfortunately, the problem is still there: engine dies when alternator starts charging.

    So the regulator isn't the one at fault.

    As Mr. Ola seems to have experienced a fault identical to mine, I've turned my attention back to the Hall sensor:

    However, I'm trying to trim down on wallet-bashing the problem until it gets fixed. Got no cash to spare. To test if my sensor is indeed affected by the alternator's EM interference, a local friend who owns an R80G/S suggested that I magnetize the rotor individually by doing the following:
    • disconnect from the alternator:
      • the three-phase current wires that run up to the rectifier bridge
      • the DF line
      • the left-most connector
      • alternator.jpg
    • prepare a DF line directly from the battery to the alternator; leave it unplugged
    • start up the bike
    • connect the makeshift DF line
    This should magnetize the rotor while leaving out the rest of the charging system. If the bike dies when I connect the DF line, then the sensor is indeed too sensitive. If the engine continues to run, I can rule the sensor out.

    Any thoughts on this approach?
    #55
  16. bmwrench

    bmwrench Long timer

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    Yes, that will work, but it seems strange that only your bike would have this problem.
    #56
  17. Muravey

    Muravey Folk you.

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    Very reasonable comment. There is almost general consensus on this.

    The replacement sensor I used is a Hüco-Hitachi HC138154. Reposting this image:

    IMG_20190820_165230.jpg

    Got this one because it was the quickest available option. Whether or not it's too sensitive to be running next to an alternator - I have no idea what to think anymore.
    #57
  18. Warin

    Warin Retired

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    Complexity 100 for what is as simple thing to do.

    I would simplify it:

    Disconnect the Df wire at the rotor. This will stop the alternator from working, the bike should then run off the battery for quite some time. If the problem remains ... I suppose the rotor could still have residual magnetism that can cause the alternator to work to some degree.. so only then would I disconnect the other 4 wires from the stator.. If the problem remains then it is probably not the alternator charging that is the problem.

    If it does stop the problem and you are convinced it is the Hall Effect Sensor/Switch .. then ask your friend with the R80 G/S to fit and try your bean can on their bike. If it works on their bike then it is not the bean can. You can mark their bean can before removal so it goes back for the same timing. Set your bean can on their bike to the same location, it will be close enough for testing. Yes, your bean can is swapable with theirs.

    Note on setting timing without a timing light: I would adjust the bean can for max idle rpms, not for an idle speed. Once at max rpm I would retard it a little, but not much.
    #58
  19. Ron50

    Ron50 Long timer

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    Theoretically, would having the battery in backwards cause a problem like this?

    As the charge from the alternator increased it would work against the battery, cancelling it out and killing the motor.

    That was the first thing I thought of.

    Or could the charge from the alternator be being "rectified" in the wrong direction against the battery voltage?
    #59
  20. Warin

    Warin Retired

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    If you did that the diode board would conduct battery voltage into the stator. Lots of smoke..


    Again, same as above. Smoke.
    #60
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