Hi, I wonder if anyone can offer any help with my poorly nc30.
Recently took out bike as it hadn't been ridden for approx 6 weeks.
Once bike was warm after a few miles, revved it through the gears up to around 12000 rpm and then it suddenly developed what I thought feeled like a lack of fuel, sort of misfire under load.
I re-fuelled bike but the problem is still there, basically if I try and rev it past 6 thou it feels like it's running on 3 cylinders, this is also true if I put it into higher gears and try to accelerate the engine again feels as though it's running as above???
I checked the exhausts and the rear riders right cylinder exhaust definitely felt a touch cooler than the others?
I took out the spark plug and it looked an ok colour and was not wet with oil or fuel, I'm wondering whether it could be a duff plug/lead, but I'm getting good sparking to frame turning over engine with plug against framework?? I have no spare plugs to try and don't want to throw money at new plugs in case it's not them at fault.
Any suggestions/guidance would be most appreciated!!
Thanks.

Hi, just wondered if your speedo is still working ok? Other things to maybe look for are a cracked vacuum line to the fuel tap or maybe a sticky needle valve in the carb?
You could take spark plugs out clean them and swap them round keeping note of were you put the suspect one.
Hope it helps

Start engine and monitor battery voltage while running above 5000 rpm.

Thanks for reply guys, speedo working fine and vacuum pipe ok. Ruling out jet problems,what sort of volts should I be getting at 5000 rpm and I assume this should be constant??
Cheers.

No more than 15.

Checked voltage @5000rpm reading 13.95v. This is bang on for rectifier output.
Any other suggestionsuggestions? ??

IMHO voltage a little low but better than >15 volts. Is bike a Japanese grey import?

Yes it's a 91/92 model according to frame/engine no,s.
Thanks.

As alluded to by morespeedvicar, Japanese bikes have speed restriction system that operates via the speed and cuts rear cylinders above 130km/h. If the restrictor becomes disconnected or faulty the cylinder cutting begins at start up. Maybe this is your problem.

The cut out occurs at 180km/h ordinarily. If I remember correct, when the restrictor is in some way faulty, the engine will start to stutter at 5500rpm in every gear.