BMW K bikes (Bricks)

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1Back to top Go down    Intermittent cut outs on Tue Mar 29, 2016 6:12 pm


Silver member
Silver member
I have a K100 that sleeps outside.

I had it for several years with no problems but then it started having slight hesitations when running. I could just feel a slight irregularity sometimes like it was missing a spark from time to time.

Then sometimes it would just refuse to start. I'd start fiddling with everything electrical , pulling relays and fuses, unplugging/replugging all connectors, etc. This would go on for about 15min, then all a sudden it would be perfect again and I'm off. with no indication of what it was. It did not seem related to any of the contract related fiddles because I checked every time I did something and it remained dead.

It would then run fine for weeks or months then let me down again.

LIke all intermittent faults it would never be consistent enough for me to track down what was wrong. Then one day it dugs it heels in and never ran again.

This is a total NO firing situation, not even a pop. Zero combustion until it magically ran again for a while.

This seems to rule out the usual plugs / coils / Hall effect sensor type problems. It's all or nothing.

I need transport so when I found a K75 in the locals ads I bought it and put the K100 to be fixed 'later'. Now the 75 seems to be devoloping the same behaviour, so I need to resolve the problem before I have another bricked brick on my hands.

I'd actually rather get the K100 running again, I preferred it to ride.

Has anyone had everience of this problem. I guess I'm not just the unlucky one who has got K's both showing the same problem.


2Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 6:17 pm

92KK 84WW Olaf

Life time member
Life time member
Hi Beamer,

I am in Cork and have had a similar issue with the K100 and seen it on a few others locally. Depending on which one my prime suspect is the plug connector to the Fuel Injection Control Unit under the seat. If its turning over but not firing this is a distinct possibility. The fuel pump connector on the underside of the tank is another strong contender.

Send me a PM if you can, my email address is in there and I will give you a talk through or meet up with you if you are in the city. There is a good gathering of Ks around town which has me very curious as to where your K75 came from!!


1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 58,645 now 65,500miles

3Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 6:31 pm


Silver member
Silver member
Thanks for your suggestions.

EFI connector, no. It's one of the first things I check and has been in and out a dozen times without effect. WD40 also but contacts were clean.

It could be a cabling fault but having spend 7 days trying to tack that down was where I gave up and bought another bike. It was like: well it would be quicker to rewire the whole bike than poke about like that forever.

Fuel pump connector, no, since it was running the pump up to pressure and then stopping the pump. Still not the slightest firing.

It could be a brake in a cable somewhere or a corroded connector. But I spend a while tugging everything around ( before it finally gave out ) in an attempt to provoke the fault and localise it. I never manage to induce a misfire.



4Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 6:45 pm

sidecar paul

Life time member
Life time member
Have a look at the connector from the injector loom to the main loom. It's under the tank and is somewhat hidden from view by the main loom.

Dirty contacts there once caused problems with my outfit.

Just another possibility.

Good luck,

'84 K100RS (0014643) (owned since '85), 86 K100RS (0018891) with Martello sidecar (built as an outfit in '88),
'51 Vincent (since '67),'72 Montesa Cota (from new), '87 Honda RS125R NF4 (bought 2015)
....No CARS never ever!

5Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 7:45 pm


Life time member
Life time member
It will be the ignition switch. Its a common problem. The contacts are coated with dielectric grease which after 25 years seems to go solid. Its an easy fix.
Cleaning a BMW K bike ignition switch

And here's my post with more pics and info
Inside the ignition switch

Last edited by Kaptain Holister on Tue Mar 29, 2016 8:01 pm; edited 1 time in total

1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90

6Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 7:55 pm


active member
active member
It might be useful to determine if it is a spark problem or fuel injection problem. Are the plugs wet ? Is fuel actually getting to the injector rail ? Do you have spark ? Figuring out what you don't have will narrow your focus to find it .

Good luck and don't give up !


7Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 8:40 pm


Life time member
Life time member
Sounds almost like the problem I had with the ignition switch on my K75RT. Intermittent problems with starting, and momentary shutdown when running. Got more and more frequent until I was having problems every day in the middle of a trip 2000 miles from home.

Here is a link to an article on cleaning that switch.

1994 K75RT
1994 K75S
1992 K100RS

1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175

8Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 9:29 pm

RicK G

Sure sounds like an ignition switch problem to me. Its easy to look and even easier to fix.

If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now

9Back to top Go down    Re: Intermittent cut outs on Tue Mar 29, 2016 9:34 pm


Silver member
Silver member
Thanks all. The ignition switch looks like a credible diagnosis. I had been considering that on the K75 because I note momentary loss of lights on the dashboard with the misfires, indicating a fairly centralised break in the power.

I don't think that fits the symptoms for the K100 but one thing at a time.

Thanks for the help.


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