Fuelling problem!!! Anyone heard an engine do this before???

Let me know if you have ever heard an engine do this, and what the fix was. The bike is a ZX6R B1H (fuel injected) I sent a letter to FastBikes last month and they posted it in the Technical section this month. Their suggestion was the alarm playing up. I have moved the alarm and it has not helped.


The symptoms are:

· Juddering in every gear at precisely 9.900rpm,

· Perfect fuelling at every other rev range,

· Does not judder when cold (after 3/4 minutes the juddering starts)

· Spark plugs are new,

· No warning lights,

So far i have tested:

· Fuel pump (changed, no difference)

· ECU (got an AA technician to test with diagnostics software etc.)

· Alarm (relocated, foam pad added to stop harmonic resonance)

Other than the alarm, there are no other electronic mods. I have an Akra exhaust, but that has been on for nearly a year and the bike was fine before. Air/oil filters are clean.

I’m all out of ideas. Please post this to and garage/mechanics you know as I’m considering part ‘ex-ing it (which would lose me about £1500)

Whoever diagnoses the problem will receive a cash reward!!! That’s how desperate the situation is!

Interested to know how the AA tech was able to test your ECU as they don’t usually know a thing about bikes.

Do obvious first like clean air filter, check coils, regulator rectifier, alternator.

I would find someone with a working version of the same bike willing to swap parts to test, and start with the reg rec then the ECU.

Oh yeah, try completely un installing the alarm and trying.

Is it a Datatool?

may be wrth contacting this poster as seems similar to see if they remedied it



This is the Kwak kidz of all things Kwak…
That’s far too smoothly rhythmic at a set point, so its not a blocked carb, or a fuelling problem, less that’s built into the bike to get her through the MOT … manufacturers know what rev range they check so they do ensure it isn’t “too mad” at that point…

I’d say Fro’s on the money… sounds like electronics are doin something…
can you reboot an ECU…? If the Kwak bunch can’t shed some light on what it might be, I highly recommend Ralph Lo Tuorco at SBK bikes in the City… he’s got an in-house Dyno and knows his onions…