Cbr400 nc23k holding back at 12000rpm
story goes as follows..

New plugs(irradium)
carbs clean as a whistle(standard jetting and exhaust and airbox)
pilot screws at 2.5 standard.
float heights at 7mm
bike starts with no problems and idles well even when cold,and pulls like hell all the way up to 12000rpm in every gear where it hits a flat spot.??
think maybe its a bit lean?what do u guys think??
if u change gear,again it pulls like a bat outa hell..until 12000rpm again..
suggestions plz guys??
thanx!!

does it do like a cough and splutter at 12000 then pick up speed again?
Have you balanced the carbs after cleaning?

Mine use to do the same thing untill i balanced the carbs.

it just doesnt wana go past 12000..
once i change gears its off like a rocket again.
its not a problem until u in top gear,where u need those extra revs
i have balanced carbs with a drill bit as close as i can get em(havent got gauges)

never heard of the drill bit method :S

Is your bike restricted at all?
what colour label is your cdi box?
You might be getting finding someone close with the guages and balance them properly mate

i think it is restricted..
i havent taken it past 180kph,so it very well mite be..
its a blue label cdi,although it used to rev right past redline.
no one i know has gauges,but i work at an engineering shop,and do have access to harris gauges which work on vacuum,was thinkin about usin those.the only thing is what size r the vacuum holes in the carb itself and what thread?i can make up some fittings if i know what size

Well the vacuum holes arent on the actual carbs they are on the inlet pipes of the cylinder head, if you look there will be 1 philips screw on each inlet pipe, thats were they go.

Not too sure on what size they are to be honest, were about in the uk are you?

If you can try get your hands on a gold label cdi, as far as i know the blue label is restricted.
If you cant get a gold label one i think one of the guys on here use to sell a mod with instructions on what to do to de-restrict it his name is leopard_pagan, not sure if he still does them though, but there is a mod you can with a resistor and splicing a few wires.

oh i forgot to mention aswell you might have a disk in the speedo with restricts it aswell and stops the top speed.

not 2 worried about restriction 4 now..180 is enough 4 me,especially on south african roads..just really want it 2 rev cleanly up 2 redline

Sounds like fueling, have you changed anything?

Wozza wrote:Sounds like fueling, have you changed anything?

when u say changed anything,u mean jetting?
all standard as per haynes manual.
bike is standard
should i try shinning the needles up by 0.5mm?do u think this would help my problem?