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Thread: K 100 RT electrical problem - help please!!

  1. #1
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    K 100 RT electrical problem - help please!!

    Hi folks

    Your help is appreciated - has anybody had one of these? Its an 86 D plate Civvy K100RT with 51k - 9k of that done in the last 8 weeks.

    Problem started when this time last week, the indicators started not to go on first time when pushed. Just ignored it at the time and pushed harder. Problem gets worse over a couple of days and then indicators work when pushed but not when i let go of switch. Then the same but sometimes both tell tale dash lights come on at same time. Then couple days later, stop working again and whenever you try to make them work, the odd time they will but the sidelight, headlight and taillight go out.

    Dont know how i found this out but at the time, sounding the horn seemed to cure / reset the problem and indicators were fine for a few hours.

    Then idicators not working more often, and this also now includes the lights (at all), the horn and also the starter button. Again, may be a a fluke but when bike didnt start, i could only think about putting it in gear and rocking it and then it started but i may have started 2nd time without doing that.

    Now i cany use it as (obviously i need indicators) but more so cause im an instructor so cant have an unroadworthy bike.

    To me, it sounds like a bad connection somewhere, cause just to see, i rode with my left thumb on the horn switch for about a 1/4 mile and then it (the horn) 'stutters' into life.

    Im completely useless with this kinda thing so i REALLY need your help please.

    MODS - PLEASE MOVE IF I HAVE PUT THIS IN WRONG SECTION, but PM me so i can find it again.

    Thanks everybody, hope you can help.

  2. #2
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    sounds like an earth failure, check earth connections to the chassis and battery

  3. #3
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    What he said.

    The switch gear has separate and isolated connectors for each side of the handlebars..........



    so if both sides are playing-up, it's likely to be something that they have in common, the main earth point.

    Remove the tank and look at the main earth....




  4. #4
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    Thanks Am i just looking for it to be loose?

  5. #5
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    Quote Originally Posted by Turraloon View Post
    Thanks Am i just looking for it to be loose?
    Maybe. More likely it's dirty.

    Undo the nut, pull the connectors away, get some abrasive paper and clean the connectors until clean metal is visible. Clean either the frame where the contacts sit or the bolt thread and the frame thread into which the bolt goes. Slap some vaseline over it when it's all back together.

    You can switch the ignition on with the tank off to test that the handlebar controls all work before putting the tank back again.

  6. #6
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    Ok, thanks very much. The tank just lifts away doesnt it?

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    There are two push-on circlips at the back, two fuel lines on the front left and one electrical connector.

    The two pins on the underside of the tank at the rear, locate in two rubber grommets and held by the two circlips.





    The two fuel pipes are just held by hose-clips to these two pipes (the pipe sticking downwards in the background is the fuel-tank breather. It doesn't have a pipe but has a small catch-trap and pipe attached to the frame below it).



    The electrical connector is usually cable-tied to the frame (down-tube to gearbox) on the right side.

    Don't be put off if the tank doesn't just lift-up easily: The rubber grommets can grip the two pegs surprisingly hard (especially after age and heat over the years has done it's job). Use a suitable lubricant on the grommets before you put the tank back on because they can be a bugger to get the pins far enough through to slip the circlips back.

    Sometimes the circlips are missing because they are fiddly to re-fit, get lost or ham-fisted people bend them. The tank will stay put without.

  8. #8
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    Your problem is the starter motor - replace the starter motor brushes and everything will be back to normal.

    They also act as earths causing the problems you have when they're worn at the limit.
    All your BMW servicing needs at the .gsshop.biz, including 1200 models

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  9. #9
    skywalker
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    Quote Originally Posted by Steptoe View Post
    Your problem is the starter motor - replace the starter motor brushes and everything will be back to normal.

    They also act as earths causing the problems you have when they're worn at the limit.
    Also give the armature a quick wiz over with some fine scotchbrite & make sure the grooves in the armature are not carboned up - if they are clean 'em out with a stanley knife blade.
    Make sure that the area where the starter motor makes contact with the gearbox casing is corrosion free.

  10. #10
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    Had exactly the same on a K100 - as Steptoe says it's the starter motor brushes.

  11. #11
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    Away to tackle this job tommorow to get the old girl back up and running.

    Checked a couple of times since my last post just to make sure that it hadnt miraculously started to work again but alas, no.

    It now wont even start now (i.e. hasnt been this bad before but seems to get progressively worse) Now wont start (plenty of battery and when you press the starter, it gives the usual Bzzzzzzzzz) and wont indicate without holding down the button and no horn and no lights.

    Do we still think its just the starter motor brushes? Or are we thinking its the main earth as Mike P said?

    If its the starter motor brushes, is this an easy job for a ham-fisted twit?

    Ta, Dave

  12. #12
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    Go with Neil's answer. He's got a lot of experience working on these for a living. Me? I'm just a tinkerer.

  13. #13
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    Quote Originally Posted by Turraloon View Post
    Do we still think its just the starter motor brushes?
    Keep asking the same question and the problem will go away.
    All your BMW servicing needs at the .gsshop.biz, including 1200 models

    Recommended as an "excellent independant" in Ride magazine 2009.

  14. #14
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    same problem

    hi, i have the same problem, bike start with frowing indicator on later he just stay on all the time then all lights go off and now nothing only lights what are working is parking light and clock.
    i change the brushes and nothing, i change starter for difrent(working order one) nothing, i check all connections cables and didnt find enything. I found i problem as on wiring harness have empty plug for optional heathed grips with brown and green/black cable and they are connect somewere(and they shouldnt be) i check it all and find out it getting wrong connection from speedo as when speedo i disconected the plug is fine. now question were speedo get wrong connection(speedo is good as i check on working one form anader bike. any ideas? please help

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