hi, don,t know if anybody can help on this very strange problem,but have an 1991 nc30, that has been running ok, but has developed a misfire between 9-10000 rpm then it pulls great right thru revband? Misfire only occurrs when bike is under load, eg (on the road),this does not happen if bike is revved whilst at standstill?
Bike was set up and used, with a tyga type race exhaust with hrc jet kit and air filter and performed superbly,but to try and eliminate problem have reset everything back to standard including carb jets ,exhaust,but still has misfire between 9-10k and as said only under load?
Have checked fuel tap,carbs, plugs, charging, airbox etc but cannot see any obvious fault?
Could anyone suggest anything to check as i'm pulling my (greying) hair out!!!!!!

any help greatly appreciated,
tom.

Check Needles and there height,

how many washers are in there?

hi do you know what the correct height is for the standard items? Bike did have a hrc set(together with a different filter)in but as said these have been removed and replaced with standard items, to try and sort out this flat spot. Could it be anything major such as A valve

thanks again for any help
tom

tomtom65 wrote:hi do you know what the correct height is for the standard items? Bike did have a hrc set(together with a different filter)in but as said these have been removed and replaced with standard items, to try and sort out this flat spot. Could it be anything major such as A valve

thanks again for any help
tom

When you say HRC what sizes are they?

a FULL HRC set up jets needles etc are like rocking horse shit for original ones, aftermarket ones are availble but you need to be running a hell of a lot of mods for these to work right,

id guess you just have STANDARD 120ish Dyno or Keihin Jets, and standard needles and someones fobbed you off with HRC and charged you a premium!

so what needles and jets do you have fitted sizes? pics would also help

Rick

Hi and thanks for the help.will have strip carbs to check existing jet/needle sizes and will post to let you know as to what it was running on. Still can't understand as to why the flatspot has developed as it was running fine beforehand. Could it be anything major such as valve or maybe ecu/cdi fault?
Thanks
Tom