Jerky at 30-50 km/h

[Galbert]

My SX-SE is very bad at speeds between 30-50 km/h. Unfortunately, it is necessary to keep this speed in most Swedish towns. When driving in gear 2 or 3, the engine can not keep constant rpm, and is very jerky, (I really don’t know if “jerky” is the right word in English. The engine differs all the time between pulling and engine breaking) even though the throttle is kept the same. There is a heavy jerky movement in the drive chain, and I am seriously worried that, in the long run, the bearing at the outgoing gear will be damaged. My Kawasaki dealer says it is due to that the speed is right between the "idle engine" and "the normal engine" (I never knew there were two engines ;-)). "You can not do anything about it," he says.
I have searched the forum for others with similar experiences, but found nothing.
Feedback from other users would be much appreciated. If it is only my bike that is doing this, it's definitely something wrong.
I am quite desperate. It is very annoying!

[roadczar]

I have not noticed it on mine. What gear are you in? Have you tried shifting to 1st? 30 kph is under 20 mph which is very slow. One thing I noticed is how tall first gear is compare to my other bikes.

[Galbert]

Thanks for your answer.
Normally I go for 2:nd of 3:rd, but it’s the same in 1:st. Most towns in Sweden is 40 km/h now, and 1:st does not feel right all the way through a town, several km:s. It’s a little bit better when the engine is cold, but as soon as the engine is at working temperature it’s the same again.

[THOR]

i am assuming its just the o2 sensors, they are not wideband and they would make the bike struggle

[cOoTeR]

Try changing your engine braking setting. If that doesn't work try getting the bike tuned.

[Galbert]

Tanks for all suggestions.
I have tried all the different settings for power, engine break and so on. Nothing helps. My dealer says there is nothing to do. Is it possible to test the o2 sensors myself in any way?

[Galbert]

Sorry cOoTeR, didn’t answer about “getting the bike tuned”. Again, my dealer says there is nothing wrong. The “tuning” you mention, is it something I can demand to be done? Is it an expensive process?

[vcyclenut]

It sounds like the bike switching between closed loop and open loop. O2 sensor on vs o2 sensor off. It was not that pronounced on my bike stock. This is usually the issue when a bike is hunting for a speed at lower rpm's like your describing

if this is it you should be able to correct it by putting the bike at a different rpm.

Nothing on the bike tuning is done by speed. Its always best to use RPM as a reference not speed when discussing issues.

if you find changing your rpm by using a different gear fixes it a new o2 sensor would likely solve your issue.

[Galbert]

Hello vcyclenut. Thanks for all advice.
Like you say the problem is depending on the rpm. In 1:st it is less problem, but like I said, it doesn’t feel ok to go several km:s through a Swedish town in 40 km/h. I mean it is as worst in 3:rd, and in higher gear the rpm is to low for the engine. I think the rpm is about 2500 when the problems at as worst.

[vcyclenut]

My guess is a an o2 sensor not out of spec enough to throw a code but it is sending bad voltage signals back the ecu causing an overly lean condition when it is on. then when it turns off the fueling cleans up and the bike makes more power.

so when its on you slow down, when it shuts off you speed up,

when your riding right around the switching point the bike will hunt for a speed as it cycles on and off, very aggravating, and not at all normal for this bike