i have a g reg cbr400 nc23 ive changed the air filter,fuel filter, plugs then got it legal, took it out today and if you get it to about 8-9k it holds back and misfires but if you push through it then it goes like hell any ideas thanks

Through my own personal experience on my NC23 running poor in that area. It turned out to be a fueling problem. The fuel pump was faulty and not pressurizing completely. (kept clicking/buzzing if you bypassed the relay and just let it in run with the bike switched off)

thanks all try thatif anyone has any more ideas that would be great

ive had all plugs out checked them for spark and all fine ive checked all pines are on and they are has anyone got any ideas what it could be cheers