hi i have a cbr400rr nc29 1990 i broke down a while back and have never really found the problem, while driving the bike cut out and decided not to start again until the next day it started fine with out a problem,
from then on the bike has never run at it original rpm of 1300/1200 rpm, and now all it wants to run at is 1600rpm thats the lowest it will go the idle seems very slow as if the bike wants to stall.

I have done the valve clearances, balanced and cleaned and sealed the carbs, check every connector for wear,check resistant in every place possible, volts check every bit of wiring loom for splits breaks in wires and resistance back to the ecu everything is sound, checked primary and secondary coil pack resistance, check ht lead the whole lot everything has been done properly, no air leaks no blocked jet nothing, pick up resistance is fine, cleaned and oiled the air filter, change the spark plugs, fuel filter, made sure the fuel pumps working, all good

but the bike still wants to run at 1600rpm, but its hard to explain just by words but at 1600rpm the bike sounds like its idle extremely slow, and not in control of its idle and when it wants to it will just cut out and die, but it will start back up again.

The idle sounds great at 2000rpm perfect as if it was running at its correct idling speed of 1300rpm, there is spark but it is extremely weak, doesn't even have that pinging sound you would normally hear from the spark, even when i rev the bike up it seems to get a little strong but not to what the spark should be like, the bike does rev through out the whole of the rev range extremely well in neutral, i have not drove the bike recently because it was quite difficult to change gear while riding at what seemed to be a steady idle of 2000 rpm,

but while riding at a idle of 2000 rpm i had this problem, each thousand rpm used to be 10 mph, so for example i would be sitting at 30mph and the bike would be reving at 3000 rpm or 50 mph 5000rpm, think you get the drift of what i mean, well now instead when im doing 30 mph it is now reving at 4000rpm or 4500rpm always 1000rpm higher then what it used to be,

I have not changed any parts everything is still the same as before when it was running fine.

Thanks for reading my life story guys any information will be much useful to me

so..


what about it is not standard?

you sure it has the right tacho on it? you sure the pickups are all good?

the plugs? the leads?

some of the symptoms cannot relate to speed can they? The gearbox runs the speedo so how are the revs out?

Bad electrics IMO....

CMSMJ1 wrote:so..


what about it is not standard?

you sure it has the right tacho on it? you sure the pickups are all good?

the plugs? the leads?

some of the symptoms cannot relate to speed can they? The gearbox runs the speedo so how are the revs out?

Bad electrics IMO....

thank you for the reply.

the clocks are standard and have not been touched

pick ups have been tests reading at 402 resistance (cold engine) which haynes manual states has to be between 380 to 420 on a hot engine it when up to 480 is this ok ?

coil packs secondary and primary were in spec and great

spark plug gaps in spec and new (ngk iridium)

charging rate good and battery voltage good

throttle position sensor greens earth, yellow would sit at around 5.00 resistance, red wire would raise in resistance when throttle is opened is this ok ?

only thing i cannot and have not tested is the ecu, all ignition wires have been tested back to the ecu and are fine

CMSMJ1 wrote:
some of the symptoms cannot relate to speed can they? The gearbox runs the speedo so how are the revs out?

.

because before i had this problem with the bike cutting out while i was riding that is what the bike rpm would sit at, for example 30 mph at 3k rpm before, and it run beautifully before so im going on how it running before it broke down, and iv owned the bike for 2 and half years.

most importantly just the idling situation is what bugs me the most, before hand it would sit at 1300 to 1200 rpm and would idle beautifully, but now it idles good at 2000 rpm and the lowest i can turn it down is 1600 rpm, but for some reason at 1600 rpm the bike would either stall or just sound like it wants to stall.

is there anyways of me testing if the rev gauge is functioning correctly ?

Goodevening, sounds like the prob may lie betwen the ecu and the pickups maybe something is breaking down underload but still giving the correct readings when tested my trident had a damaged coil pickup but checked out ok replaced this from another bike and it fixed prob.May be worth taking cdi to a honda dealer to get checked over they should have the test gear, or even a dyno run to look at fueling and ingition curve this may help with diagnostics,regards craig

why do you keep posting the same thing in different threads (which i have to keep moving to the correct sections) I have edited, merged and deleted around 4 of your random threads now.
Why not just stick to one thread? it's not difficult, we all seem to manage it (well most) quite well.

CRM wrote:why do you keep posting the same thing in different threads (which i have to keep moving to the correct sections) I have edited, merged and deleted around 4 of your random threads now.
Why not just stick to one thread? it's not difficult, we all seem to manage it (well most) quite well.

What i told him last night mate, and he still made another new thread about the same problem again today.
Quite annoying actually seeing this same problem posted over and over again.

CRM wrote:why do you keep posting the same thing in different threads (which i have to keep moving to the correct sections) I have edited, merged and deleted around 4 of your random threads now.
Why not just stick to one thread? it's not difficult, we all seem to manage it (well most) quite well.

you locked my last thread, so i change it to this section of the forum thinking it is the right section am i wrong again ?

CB 4 wrote:Goodevening, sounds like the prob may lie betwen the ecu and the pickups maybe something is breaking down underload but still giving the correct readings when tested my trident had a damaged coil pickup but checked out ok replaced this from another bike and it fixed prob.May be worth taking cdi to a honda dealer to get checked over they should have the test gear, or even a dyno run to look at fueling and ingition curve this may help with diagnostics,regards craig

Thank you.

Now some one talking on my level and not thinking its an air leak or blocked jet.

i have just removed the cdi to get checked tomorrow at honda dealers, see what they can do for me.

i do have a spare pick up there off a running bike i am thinking of changing it over but i am going to see what the honda dealer says.

i do think the same as you either its the cdi or the pick ups, but i just wanted some reassurance from some one on this site that might know more about the issue, and that has maybe experienced this problem before, now i am just going to start changing things over on the ignition unit till this beast works again,

bike has done me proud for 3 years of abuse from myself, so i will not give up when i say abuse i mean poor thing doesn't go a day with out getting a thrashing but thats why these babys were made, and thats why i look after it with regular servicing keeping this TROUSER FIREWORK going strong.

thats why i know its an electrical fault not an air leak or blocked jets, which in many cases it is but this one is for sure not the case.

Thank you for the reply

Riccodan wrote:

CRM wrote:why do you keep posting the same thing in different threads (which i have to keep moving to the correct sections) I have edited, merged and deleted around 4 of your random threads now.
Why not just stick to one thread? it's not difficult, we all seem to manage it (well most) quite well.

you locked my last thread, so i change it to this section of the forum thinking it is the right section am i wrong again ?

No, i locked one because you reposted the same a week later after not bothering to even come back to the forum and read the replies to your original post.
Then i removed the one from general, ride outs, and NC30 workshop again all the same posts just in random sections.
and as for changing to this section - wrong again, i had to move it to here from general again.

And as for the original question. are you sure its not an air leak from the carb rubbers ? or incorrectly assembled carbs / float heights ?