Hi i recently purchased a cbr 400nc23 and it has a running problem .
when you start the bike all is well there's no smoke our funny sounds , and when you get on and ride away it runs perfectly at low revs (unfortunately for me as the test ride was at low revs around the block)
Its only when you travel up through the rev range the problem comes ,its almost like I'm running out of fuel the power is on off on off on off like I'm feathering the throttle if you open her right up it does power through but the hesitation feeling just picks up speed
Any ideas or advice as to what may be the cause would be greatly appreciated thanks

Have the same problem with mine. Cleaned the carbs and changed the fuel pump but made no difference. I have took out the fuel filter and run the line staright from the tank to the pump which hasn't cured the prob but it is about 70% better.

i would be inclined to say its definately fuel related......
im guessing it happens all the time,usually intermittent problems are possibly electrical but this to me sounds like carbs are needing a clean or something similar.
check all hoses etc.


william

I'm not sure if this is a fuel problem iv done all the usual checks
I was thinking could it be this restriction on the revs i have read about on here the problem does seem to start at about 5000rpm and stay all the way to the red line.
The only thing I'm not so sure about is.
This restriction is the cdi unit cutting the supply to two of the spark plugs when the bike arrives at the top speed limit . But if this system fails for some reason the cdi unit cuts the supply to the plugs at 5000rpm.
so if in both cases the method of restriction is the same would the bike stop accelerating when i reached 5000rpm as it would when working correctly at the top speed limit because although my problem does seem very similar to the ones i read about with this revs problem i am able to continue accelerating past the 5000rpm mark .

Any idea how to find out if this is my problem or am i barking up the wrong tree THANKS

1st question.. what exact model is your NC23? only the 1989 NC23 has this restriction in the speedo/cdi.

if your bike is the 89 nc23.. heres what you need to look for:
is the speedo all plugged in?
check the main fuse box for the dash fuse if its blown
has a de-restrictor been put in place and come loose, check behind speedo AND at the CDI?*
has any wiring from the speedo to the CDI come loose, shorting out, looks dodgy?


*look for a resistor or a small black sealed box.

hi my bike is on a E reg i havent yet recieved the log book so i am not sure of the exact age but im sure it has the little black sealed box behind the speedo . im sure the fuses are ok all the dash lights still work including the 50 mph light but i will check all the wiring condition and post my findings

what kind of speeds can you reach?
if it was the restriction problem then the bike would be running on 2 cylinders and it would be very difficult to pick up much speed............

william

if this kicks in at 5k RPM it will struggle to get past 30mph!

BTW all we'd need to ID the bike model is the frame number...
model-----------year---Frame num
CBR400RR-J 1988 NC23-1020001 to 1036454 = Triarm J NOT restricted
CBR400RR-K 1989 NC23-1090001 to 1098116= triarm K 112mph restricted
CBR400RR-L 1990/91 NC29-1000001 to 1010598 = Gularm L 112 restricted
CBR400RR-N 1992/93 NC29-1050001 on = gularm N 112mph restricted
CBR400RR-R 1994/95 NC29-1100001 on= gularm R 112mph restricted

right the small black box behind the speedo.. check thats its plugged in properly (see the link below for the right wire colours), has the wiring come loose?
you can bypass the box for now, plug the original plug BACK in to the speedo... get things running again then worry about the speed limiter later which should them kick in at 112mph (180Kph). there are a few other ways to bypass this.

if the fuse that also runs this blows, it normally kills the dash lights, horn, headlight, tail lights.. if all that is still working then its not the fuse.

http://i18.photobucket.com/albums/b145/ ... NC23-K.jpg" onclick="window.open(this.href);return false;

simple as this...look at the cdi...if it has a gold label its not restricted...if it has a blue label...it is
job done
stimpy

true, but it doesnt tell the chap what model of NC23 he owns...