BMW K bikes (Bricks)

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73MOH

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A few days ago my 1100 started to start a bit slow...

then one morning the motor struggled to hold revs on the highway.... limped to work.

checked battery, 12.5v standing, 13.5v running , but dropping to as low as 9v during start, found a loose terminal and thought that was the issue..

motor completely broke down on the way home, it would start(slowly) and run, but not sustain any rpm.. 2 tow trucks later..I was home.

next day I installed a new battery, hit the start button, it tried to crank slowly and let out a bit of a squeal, then I lost the starter, but could still hear the relay... then after a few attempts, the starter relay stopped aswell.... then the instrument and headlights started to play up... (loadshed?)

I clicked it up to fifth gear and tried to turn the rear wheel by by hand... it will turn forward with lots of effort, but backwards takes all my strength... but weirdly by jarring the wheel, It will cause my instrument and headlight to flicker back on...

Registration is due next week, so I kind of want to establish this weekend if the motor has a major issue...
planning to remove gearbox, clutch, sprag, alternator and spark plugs and see how free the motor is... unless anyone has a better idea?...

the video below is one I found that sounds eerily similar to mine.... his problem turned out to be terminal.

https://youtu.be/k9SEV2YVLvc


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Paul
1986 K100 RS
1997 K1100LT
2005 KTM990sd
    

92KK 84WW Olaf

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Starter motor brushes? Starter motor issues? It can cause lots of electrical issues like you describe.

If you have ABS1 as in K1100 up to 1994 its easier to get the starter out.


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1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

73MOH

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@92KK 84WW Olaf wrote:Starter motor brushes? Starter motor issues? It can cause lots of electrical issues like you describe.

If you have ABS1 as in K1100 up to 1994 its easier to get the starter out.
Thanks Olaf... Will definitely thoroughly investigate starter before proceeding ... it's a 97 with abs 2... I did the clutch not long ago, it's a bit pain, but not too bad.


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Paul
1986 K100 RS
1997 K1100LT
2005 KTM990sd
    

92KK 84WW Olaf

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Check all your connections etc first. I know that to get starter out you have to remove the ABS modulator so as you say, a pain.

Keep an eye out here as a lot of the guys know more than I do. But it does not sound like mechanical problems in the engine.

I have 13.6v at rest on my K1100LT. But it does not drop as far as 9v when starting. I have had instances of new batteries being stuffed so even though its new its not quite a guarantee its actually perfect, in two or 3 cases they were bad and failed load tests.

The struggle to start would suggest starter is not getting the required current, either bad earth connection, lack of battery, faulty relay, fault in starter as in brushes/commutator would be places to look into. I probably would leave taking the starter out until last, if you do have spare relays its worth swapping them to eliminate them from the cause. If you have a fully charged battery, it should of course turn over very nicely.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

RicK G

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When you try to turn it backwards the sprag engages the starter that is why its hard to turn. Also it should charge more than 13.6 volts 14.0 to 14.2 is the ideal. At 13.6 the battery will probably not be getting a full charge if you use it to commute.


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"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

mike d


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'I know that to get starter out you have to remove the ABS modulator so as you say, a pain.'


Not true Olaf. I removed the starter on my 1994 K1100 (with ABS2) without touching the ABS modulator. Agreed it was a bit of a pinch, but still can be done.

Mike

    

73MOH

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Thanks for pointing me in the right direction Guys....
I'm not sure this explains all the issues , but it's a good start.
I think my starter is down to one operating brush.



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Paul
1986 K100 RS
1997 K1100LT
2005 KTM990sd
    

TacKler

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I would start by giving the rotor/armature a good clean with an ink eraser. It looks way too dirty to me. There may be other ways that others will suggest.

As for the brushes, I would check how much spring tension there is. Are they worn that much that they are only lightly touching the armature and not making full contact?



Last edited by TacKler on Sun Dec 09, 2018 12:28 am; edited 1 time in total


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RicK G

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Yeah that commutator sure needs a clean but DON'T use wet and dry sandpaper as it leaves small carborundum particles embedded in the copper. Best thing is in a lathe and a very light skim or a scotch brite pad then be sure to clean between the segments.


__________________________________________________
"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

Dai

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I think I'm always the dissenting voice around here...

The commutator looks dirty but there's nothing wrong with it. The copper segments (even from new) are full of micropits. The 'dirt' build-up you see is carbon being transferred from the brushes to those micropits and producing a much smoother surface than the copper alone. That's better for the brushes. A quick twist in a tightly-held cloth should be enough to remove any excess carbon. Clean inbetween the segments by all means (use a plastic scraper as metal will cause damage) but from the pictures, I don't think that needs doing either.

Now, if there was an obvious wear track I'd definately be in Rick's camp and say 'get it skimmed back'.

Told you I was the disssenting voice! Very Happy


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

73MOH

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Well I've just done a few laps around the block ans the bike seems to be running very well .... thanks guys.
who'da thunk starter motor brushes were so critical for the well being of a k bike, has any body got an explanation why. I would of thought it would run fine without a starter at all as long as you had a hill to start it on.

On another note, does anyone know any good reason why a previous owner might would do away with the Lamp control unit and replace it with wires?(see pic)


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Paul
1986 K100 RS
1997 K1100LT
2005 KTM990sd
    

Dai

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It's all down to the 'load shedding relay'. The LSR provides power to a lot of the components on the bike and it earths through the starter motor brushes. When you hit the starter button you put twelve volts on the brushes which causes the LSR to drop out (no more earth) and the most obvious result is your lights go out. This is to give the battery an easier life. If the brushes or the commutator is in poor condition then all hell can break loose as the LSR drops in and out at random. IMNSHO this is a p!ss-poor piece of design because a far more reliable method would have been to have a relay that is permanently earthed and simply cuts the power to the LSR circuits when the starter is pressed and that relay is energised.

As for the BMU; two guesses.

1. The original died and the PO couldn't be bothered to replace it
2. You've got LED bulbs fitted - the BMU can't cope with those. The low resistance means the BMU thinks both bulbs in the tail-light are permanently blown.



Last edited by Dai on Thu Dec 13, 2018 7:32 am; edited 2 times in total


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

92KK 84WW Olaf

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@mike d wrote:'I know that to get starter out you have to remove the ABS modulator so as you say, a pain.'


Not true Olaf. I removed the starter on my 1994 K1100 (with ABS2) without touching the ABS modulator. Agreed it was a bit of a pinch, but still can be done.

Mike

This one is good to know in case I have to get in here. Do you then take out the alternator to get the starter motor out?


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

mike d


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Life time member
It was a long time ago, and I was very new to the K series. I seem to remember removing the coils, but the alternator and ABS module remained in place.

Mike

    

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