I'm hoping to call on the collective brain power for this issue that has plagued my racebike all season. At the end of last season I rebuilt the engine, just a freshen up, and when I ran it in on the dyno there looked to be a bit of a stutter once the revs reached above 12,000RPM but then recovered quickly and revved out to redline. The dyno operator wasn't too concerned with it as it was pulling nice and clean everywhere else.

During the first round I didn't notice the stutter, however during the 2nd round it felt as if the power curve would flatten out. The 3rd round was even worse. From what myself and another rider could tell is that once the revs reached 11,000RPM it would start running on only 3 cylinders.

Throughout the weekend I changed spark plugs (no change), coils (seemed to be a slight improvement, but that's subjective as I probably wanted it to improve) and HT leads (no change). I also flushed out the fuel tank and stripped and cleaned the carbies in case there was a blockage.

I've ordered a new set of OEM coils to remove any doubt about dodgy 2nd coils, but my question is whether the NC35 is also affected when the speedo is removed, does a 2K Ohm resister need to be installed or not? My understanding is that the rev limiter would kick it at 5,500RPM, not 11,000RPM.

Any help/suggestions would be greatly appreciated

You have applied the HRC mod to the fuel tap, does battery voltage remains under 15 volts at all rpm and yes RVF has speed limiter but as you say it would kick in a 5500rpm without the bypass.

Hi Magg, yes the fuel tap had been modified as per the HRC manual. Testing the battery was one thing I didn't do (not sure why as it wouldn't have been quick and easy). I'll test the battery and go through the wiring loom to look for any breaks, etc.

Is there anyway to test the engine to simulate being under load? It seems to rev fine while in the garage, the symptoms only seem to present themselves once I'm out on track, which is annoying and expensive.

What cdi are you using? Just incase it’s an ignitech as didn’t the old ones suffer an issue like this?

Hi Yakama, I'm using the standard CDI so it shouldn't be the rain for the issue... I'm hoping

I would say not enough fuel!! Have a look on the fuel lines. When it cvomes only above 11000rpm.

Michael

Thanks Michael, that was my first assumption as the issue seemed to be getting worse throughout the season. When I get a chance I'll flush the tank and clean the fuel tap and lines. The carbies will be getting an extensive clean as well.