BMW K bikes (Bricks)

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1Back to top Go down    Intermittent cut out K100 '85 on Sun Jan 01, 2017 10:59 am


New member
New member
Hey everyone, Happy New year! 

I have been reading a million posts here and have been fiddling around with my 85 k100 and the frustration is growing...

The bike would initially cut out while riding and sometimes not start for a bit. 

I started with replacing the fuel pump connector with the extra from the electrical box used for the alarm.
No change
Replaced the fuel
No change
Replaced all of the fuel lines
No change
Replaced the sparkplugs (and found shitty corrosion on the leads and cleaned with custom made tool and reinstalled)
No change
Replaced the fuel injectors $$ ugh!
No change
Replaced the fuel filter
No change
Checked the operation of the air valve, free and clear

I just tried to go for a ride and made it 4 blocks and had to start it 5-6 times.  I was hoping it was just because there was air in the filter or something... but 20 mins later after pushing the bike home it doesn't seem to be the case. 

My last step is replacing the fuel pressure regulator, but since they don't have any equivalents in stock here at the NAPA... I'm looking for some help  Very Happy

I've read up and down on this forum (BTW is there a sophisticated search tool I'm missing?) and followed every suggestion that seemed to be similar.

Thank you!!!! Exclamation

2Back to top Go down    Re: Intermittent cut out K100 '85 on Sun Jan 01, 2017 12:17 pm


Life time member
Life time member
First thing you need to do is determine if the engine is not running due to lack of spark or lack of fuel. 

I would take the cover off over the spark plugs and go for a short ride close to home.  Take a clean plug and a pair of pliers to pull off one of the plug caps.

When the bike quits, pull a plug cap and stick the spare plug in it and crank the motor watching for a spark.  No spark - your ignition system is the problem.  Spark - crank the engine some more and if it doesn't start, pull the plugs and check to see if the are moist with fuel. 

Then get back to us.

Personally, I am suspecting your Hall Effect Sensors(HES).

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

3Back to top Go down    Re: Intermittent cut out K100 '85 on Mon Jan 02, 2017 2:50 am


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Life time member
I'd also be checking the condition of the spark plugs as soon as it stalls. That will tell you a bit about what's happening.

But before any troubleshooting, make sure your battery and alternator are up to spec and clean all your earth connections and important electrical connectors.
Check your FICU (above battery) and ICU (at front under tank) plugs are clean and seated properly. These are common causes for intermittent stalling and starting problems.

Do your instrument lights go out when it stalls?

.... (BTW is there a sophisticated search tool I'm missing?) ....
There's a search bar at the top of the Portal tab

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

4Back to top Go down    Re: Intermittent cut out K100 '85 on Mon Jan 02, 2017 6:09 am

mike d

Life time member
Life time member
When the bike cuts out, do you lose all power (warning lights etc.) or just the engine. The wiring to the ignition switch is often a place where, over time, due to tight tie wraps, the wires can fracture. The switch itself can also be a the source due to dirty/worn contacts.



5Back to top Go down    SOLVED (I think) - THANK YOU FOLKS! on Tue Jan 03, 2017 2:18 pm


New member
New member
Thank you everyone for the help! 

The lights stay on when it cuts out... 

I disconnected the FICU and ICU, sprayed with connector cleaner (they were pretty clean to begin with) and resat/reseated (is that a word?) them.  
No Change

Checked the spark plug for spark... definitely sparking... but seemed not consistent. 
took one out and it was wet.

So I took all the ring terminals off of ground, there was some crud in there, but nothing major.  I cleaned with steel wool to shiny metal and reinstalled. 

started cleanly!   Went for a spin!  
WOW... something so simple, but uberly important.  
So now with a new filter, injectors, plugs yadda yadda... I have wheels under me again. 

I am hesitant to call the game done, but I feel like this quarter is complete. 

Thanks again everyone!!!!

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