BMW K bikes (Bricks)

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1Back to top Go down   1988 K100 hesitation Empty 1988 K100 hesitation Sun Apr 11, 2021 9:22 am

ush1000

ush1000
active member
active member
Hi

I absolutely love my bike but it has developed a little niggle which seems to be getting worse. 

After a blat around the country roads doing normal speeds, 50 60 mph, when I slow to pootle through a village at 30 mph the bike occasional cuts out/hesitates for maybe 1/2 second then all ok again. 

It used to do it once in a blue moon but it is getting more regular, I think the bike is warning me to investigate. It feels like an electrical problem rather than mechanical. Does this fault ring any bells with you guys? ECU TPS?

Thanks for reading

    

2Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sun Apr 11, 2021 10:46 am

Laitch

Laitch
Life time member
Life time member
If you haven't changed the fuel filter, it's time to do it.

Intermittent, brief stalls like this are hell to chase.
You'd most likely be better off by just cleaning your earth connections and electrical connections using DeoxIT D5, starting with the main ground connection under the tank, the four-pin connection under the tank that supplies the fuel pump and fuel level sender, ignition control plug under the tank, the battery earth connection on the transmission, your fuel injection control plug under the seat.

DeoxIT can be obtained on line or often at musical instrument stores that sell electrical components. It's an effective product for cleaning and protecting connectors.


__________________________________________________
1995 K75 81,000 miles
1988 K100 hesitation Usa-lo10
    

3Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sun Apr 11, 2021 10:47 am

Laitch

Laitch
Life time member
Life time member
1988 K100 hesitation 652573



Last edited by Laitch on Mon Apr 12, 2021 12:16 pm; edited 1 time in total


__________________________________________________
1995 K75 81,000 miles
1988 K100 hesitation Usa-lo10
    

4Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sun Apr 11, 2021 12:24 pm

robmack

robmack
Life time member
Life time member
I had this problem last season.  I had hesitation as well as engine stalling if I closed the throttle for engine braking when approaching a red light for example.  I don't know if you are experiencing the second symptom, however I changed out the Z-tube that connects the air accumulator to the crankcase breather and it solved my problem.  The old Z-tube looked in fine shape visually and I was certain all the clamps were snug but still, changing the part got rid of the problems for me.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

5Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sun Apr 11, 2021 12:51 pm

moriarti

moriarti
Life time member
Life time member
I had same or similar problem loads of suggestions nothing worked until Crazy Frog
Suggested ICU ignition control unit fitted at front of frame under the tank. Replaced same with S/H unit problem solved. Very Happy Very Happy


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

6Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sun Apr 11, 2021 2:02 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
How is your battery? My 1988 K100 alternator stops charging at about 1500 rpm, and the battery takes over. If the battery or the electrical connections are not up to snuff, it's possible for the system voltage to momentarily drop enough to create problems for the ECU or the injectors.

I had another K100RS16V that had a voltage regulator problem that made the system voltage drop to about 11.8 when coming to a stop after a high speed run while the regulator slowly increased the alternator output at the lower rpm. It didn't help that the battery was also a bit long in the tooth. That bike had a habit of dying at the end of expressway off ramps until I replaced the regulator.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

7Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Mon Apr 12, 2021 9:01 am

Matthew-Brisbane

Matthew-Brisbane
Life time member
Life time member
How good are your coil and leads ?


__________________________________________________
1986 K100 RS Motorsport
#### K100 RS Project 
2011 R1200 GS
    

8Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Mon Apr 12, 2021 12:06 pm

ush1000

ush1000
active member
active member
Awesome guys thanks, loads of stuff for me to investigate and get stuck into. I will update the thread if I find a cure.

Thanks again

    

9Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Wed May 19, 2021 8:17 am

ush1000

ush1000
active member
active member
@robmack wrote:I had this problem last season.  I had hesitation as well as engine stalling if I closed the throttle for engine braking when approaching a red light for example.  I don't know if you are experiencing the second symptom, however I changed out the Z-tube that connects the air accumulator to the crankcase breather and it solved my problem.  The old Z-tube looked in fine shape visually and I was certain all the clamps were snug but still, changing the part got rid of the problems for me.
Could you possibly provide a bit more detail to the part you describe as the Z tube? Thanks

    

10Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Wed May 19, 2021 9:34 am

Laitch

Laitch
Life time member
Life time member
@ush1000 wrote:Could you possibly provide a bit more detail to the part you describe as the Z tube? Thanks
If you were to click on the Portal tab at the top of this page then type z-tube or z-hose into the search box then click the Forum search button, a number of posts that might describe this part, what it does and its symptoms of malfunction would appear as if by magic, but because you have been drawn into reading this post instead, I would describe it as a short, two-angled rubber hose attached to the engine block and the airbox by means of two hose clamps for the purpose of conveying blow-by combustion gases within the block into the air intake stream for combustion. It can be examined in its natural habitat by looking for it at the top of the engine on the gear-shifter side of the moto. Please view the photo and diagram. In the photo, the orange arrow indicates the throttle switch, the green arrow indicates the coil cover and the wiggly yellow circle indicates the z-tube. In the diagram, the red arrow indicates the z-tube. The tube location is the same on three-cylinder and 4-cylinder models.
1988 K100 hesitation Z-hose10
1988 K100 hesitation Z-hose11


__________________________________________________
1995 K75 81,000 miles
1988 K100 hesitation Usa-lo10
    

11Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Thu May 20, 2021 10:55 am

ush1000

ush1000
active member
active member
Fantastic detailed reply, I like this site. Huge thanks

    

12Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Thu May 20, 2021 12:27 pm

Laitch

Laitch
Life time member
Life time member
:BW:


__________________________________________________
1995 K75 81,000 miles
1988 K100 hesitation Usa-lo10
    

13Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Fri May 21, 2021 8:53 am

crimona

crimona
active member
active member
I'd check spark plug colors. It may give a clue.
From my minimum K bike experience can be Z breathing tube or fuel injection problems.

    

14Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sat May 29, 2021 7:59 am

ush1000

ush1000
active member
active member
Ok I changed the Z pipe, tricky little sucker and so far so good. Limited riding opportunities recently, work, weather etc but it does seem to have made a difference (changed fuel filter too). The old pipe did not look damaged or blocked at all hmmmm. I can feel it wants to hesitate sometimes, reckon the fuelling could do with checking over.

    

15Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sat May 29, 2021 9:00 am

mike d

avatar
Life time member
Life time member
Could you easily blow through the fuel filter?

If not it could have been partially blocked.

Mike

    

16Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sat May 29, 2021 10:47 am

Laitch

Laitch
Life time member
Life time member
@ush1000 wrote:I can feel it wants to hesitate sometimes, reckon the fuelling could do with checking over.
Did you inspect and clean the battery's cable connections, the battery's ground connection on the transmission, and the ignition switch's connection under the tank?


__________________________________________________
1995 K75 81,000 miles
1988 K100 hesitation Usa-lo10
    

17Back to top Go down   1988 K100 hesitation Empty Re: 1988 K100 hesitation Sat May 29, 2021 11:34 am

robmack

robmack
Life time member
Life time member
@ush1000 wrote:Ok I changed the Z pipe, tricky little sucker and so far so good. Limited riding opportunities recently, work, weather etc but it does seem to have made a difference (changed fuel filter too). The old pipe did not look damaged or blocked at all hmmmm. I can feel it wants to hesitate sometimes, reckon the fuelling could do with checking over.
Long side goes to the air box and short side goes to crankcase (so that it fits under the air box). Look at the old pipe under a magnifier. If you flex it, cracks will probably appear, especially where the clamps were situated and near the bends. They don't have to go all the way through to begin to cause problems.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

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