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

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.

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.

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.

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.

How good are your coil and leads ?

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

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

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.

Fantastic detailed reply, I like this site. Huge thanks

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.

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.

Could you easily blow through the fuel filter?

If not it could have been partially blocked.

Mike

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?

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.