Rev counter issue.

[scubasteve]

Having a bit of an issue with the NC and wondering if anyone can point me in the right direction.

I started it up earlier and noticed that with the choke on whilst warming the bike up the rev counter needle was sat at 8k but the engine sounded like it was only at around 3k. I let the bike warm up for a short period and then knocked the choke off and the needle was sat at 4k but the engine was idling at its usual 1.5k ish. I took the bike for a quick ride and as soon as you give it some throttle the rev counter needle shoots round to 16k in the red line. The engine isn't hitting the limiter or stalling tho it's just the counter that isn't working. The bike did feel slightly sluggish but that could just be that it was a bit cold still.

I'm doing a bit of guess work here as I'm no bike mechanic but is this possibly a crank sensor issue or a problem in the ecu?

[Neosophist]

most likely a fault with the rev coutner as its fed directly form the ignition box.. easy to follow this wire and check it for signs of breakage.

id start though by checking battery voltage wth engine running.. if your reg/rec has gone it can melt the ignition box which will cause poor running, all sorts of electrical gremlins.

if battery is not being over-charged then check the rev-counter wire is ok, clean the plug up for rev-counter and if thats not the problem try and try another rev-counter..

not a lot can go wrong.

[scubasteve]

Ok, thanks very much for the advise,

I first checked the reg/rec as suggested and the results seemed fine. I'm getting 14.3v on tickover and it drops slightly to 14.1v when opening the throttle. The battery is healthy too. I try to check the reg/rec once or twice a year as I hear they are a common problem and can cause other parts to burn out.

I then removed the nose cone to investigate the wiring on the back of the rev counter. The wires all seem fine and I disconnected the plug which also looked ok too. There's no signs of burning around the plug or pins and no visual breaks in the wires. I'm unsure on the location of the ignition box so didn't check that but assume it's ok as the reg/rec results seem normal.

This leads me to believe that the the fault lies with the rev counter? My friend has an NC35 which I could borrow the rev counter from to make sure that it is this. Do you know if his NC35 counter is compatible with my NC30 so I can test this?

[Neosophist]

no you cant use an nc35 counter inplace of an nc30 one, it needs to be an nc30 one on an nc30 bike.

there should be 3 wires feeding the rev counter, power, earth and signal.

siganl wire comes from the igntiion box, which is at the back of the bike.

if the earth is ok and the signal wire isnt damaged it stands chance the rev counters knackered.

[scubasteve]

Ok thanks,

Now knowing that the problem is probably the rev counter, i have realised that my clocks are not standard (or at least the rev counter doesn't seem to be). I originally thought that i had standard clocks with replacement white dial fascia's. Now looking closer i have noticed that the needle on my rev counter face's directly down in the 6 o'clock position at 0 rpm where as a standard rev counter needle starts at a 4 o'clock position at 0 rpm. As for the speedo im not sure, but i assumed this was the standard speedo with a white replacement dial fascia that reads in mph rather than kph. The mileage counter/odometer still counts up in km rather than miles even tho the speedo is in mph.



Does anyone know where this rev counter may have come from? I started to think that the clocks may have come from a company selling aftermarket clocks but then saw some clocks for the NC23 and NC29 which have the same starting point for the rev counter needle as what mine is. Are the CBR400 clocks compatible with the NC30's and if so is this a possibility of what somone could of done to my bike before i bought it? I'd prefer to keep all my clocks with a white background so dont really want to have a standard black rev counter and a white speedo and fuel gauge. Also dont really want to change the speedo as its handy having it read in mph. I'm hoping that i have a cbr rev counter with a white dial replacement so that i can just buy a replacement and put my white dial out of the broken one into it but im sure this wont be the case. Any suggestions would be appreciated as im a bit lost. Here's another picture showing the back if it help identify it.

[Cammo]

The rvf and nc29 tachos are not compatible with the vfr (without loom and cdi change) so I doubt it's from one of those. Possibly an nc23 tacho but I'm not 100% sure this will be compatible with the vfr cdi either.

Best thing to do would be to open up the tacho and look for any identifying marks (e.g. mr8 code for vfr).

Sticking on the white dials is fraught with problems unless it's done properly. Each of the clock needles has some tension and rests against the stop, unless you know what this tension is you won't be able to put the needle back on in the same spot that it came off - beware!

[scubasteve]

The rvf and nc29 tachos are not compatible with the vfr (without loom and cdi change) so I doubt it's from one of those. Possibly an nc23 tacho but I'm not 100% sure this will be compatible with the vfr cdi either.

Best thing to do would be to open up the tacho and look for any identifying marks (e.g. mr8 code for vfr).

Sticking on the white dials is fraught with problems unless it's done properly. Each of the clock needles has some tension and rests against the stop, unless you know what this tension is you won't be able to put the needle back on in the same spot that it came off - beware!

Cheers,
I've managed to find a NC23 rev counter on eBay cheap so I'm gona try that first. It was the only rev counter that I could find with the same markings on the back as mine and the wiring looks the same as does the casing. If this works I will investigate further into changing dial faces but I will bare in mind what you have said about the tention for the needle. If the NC23 counter isn't a fix I will take the original to pieces and look for the identifiying marks you referred too.

[scubasteve]

Right, I have now received the NC23 rev counter that I bought as a bit of a gamble off eBay so thought I'd post my results.

The new counter looks exactly the same as my old one with the same markings stamped on the back, same plug and earthing point and same rear mounts. Swapping them over was simple and thankfully when I started the bike the needle seemed to match the revs of the engine. I let the bike warm up and knocked the choke off and the needle was idling at it's usual 1.3k ish. Took the bike for a good run and it seems that it's problem solved. I'm not sure if this means that the NC23 counters are compatible with the NC30's as my NC is not exactly standard standard, but the loom looks original so I assume it does. The new counter has a black face instead of a white one so looks a bit out of place in the middle of the other two dials so I'm now going to look into changing this. Would prefer to stick with white dials rather than the standard black.

[Neosophist]

Right, I have now received the NC23 rev counter that I bought as a bit of a gamble off eBay so thought I'd post my results.

The new counter looks exactly the same as my old one with the same markings stamped on the back, same plug and earthing point and same rear mounts. Swapping them over was simple and thankfully when I started the bike the needle seemed to match the revs of the engine. I let the bike warm up and knocked the choke off and the needle was idling at it's usual 1.3k ish. Took the bike for a good run and it seems that it's problem solved. I'm not sure if this means that the NC23 counters are compatible with the NC30's as my NC is not exactly standard standard, but the loom looks original so I assume it does. The new counter has a black face instead of a white one so looks a bit out of place in the middle of the other two dials so I'm now going to look into changing this. Would prefer to stick with white dials rather than the standard black.

Take the dial off the old rev counter and swap it over.

[scubasteve]

Yeah,
That would make sense as I already have the parts. I was just a little concerned about doing this myself after reading cammo's comment above regarding setting the tention and rests when re attaching the needle. I think I need to do a bit more research into this before taking any action.