NC30 Possible electrical fault.

[Mattzmad]

hi guys,
need to pick some brains.
started the nc30 the other day during track prep and noticed the speedo was somehow sinced with the tacho revs. (idling around 30mph lol). anyway my initial thoughts were some water had got in causing a short. so i left her to dry out in the sun for a couple of days before i retried. on the next attempt when i fired her up the speedo thankfuly wasnt making a reading but the tacho had decided to do the same. on top of that the bike fails to rev past around 5k (at a guess) demonstrating some sort of missfire and back firing. followed by a stall.

the carbs have been ballanced recently (and used ok)
battery fully charged.
speedo now removed.
i worried i plugged the rear coil in wrong but the leads are clearly different lengths so i've pretty much ruled that out.

J plate bike
i suck at electrics.

[magg]

No speedo will give 5000 rpm limit if the 180km limiter function has not been bypassed.

[Neosophist]

The speedo is mechanical, it can't read unless the drive sprocket is turning (bikes in gear and running) which drives the speedo, unless the needle is jammed.

Inside the speedo is a sensor circuit like magg has said, it's connected to the loom behind the clocks, if disconntect your revs will miss at 5500rpm.

Make sure it's connected proprerly and you havn't disturbed it.

As for the tacho being wonkey... bad earth somewhere? water in the connections?

Take apart all the blocks behind the instrumentation and spray with wd-40 and re-assemble.

You can take the speedo apart easy, it just unscrews, remember to remove the tiny screw from the trip reset knob and remove that else it wont come apart,

move the needle up and down and make sure it returns ok to zero, might wanta bit of wd-40 on the spindle if it's got wet, drive out the moisture.

Reaseemble and check the earth points and yous huold be good.

[Mattzmad]

Ok cheers guys. Ill have another tinker. Hope is now restored its not too serious.

[arsey30]

.
i worried i plugged the rear coil in wrong but the leads are clearly different lengths so i've pretty much ruled that out.

The coil sparks on the idle stroke, so the plug leads will work either way around.

[Mattzmad]

Ok guys here's where I am.
Took speedo apart cleaned it and removed the limiter plate as I was there anyway.
Traced back EVERY connection on loom cleaned and wd40'd.
Temp guage works neautral/oil lights work and yet the rev gauge still doesn't.
Bike starts on button every time.
Same thing happens. Hits some mysterious limiter splutters pops and bangs.
Has cdi unit gone leaving it in gimp sorry limp mode?
Rev gauge driven from there too?
All very odd
Seems to get very hot quickly too

[magg]

Tacho is driven from cdi not off any of the coils, maybe dud cdi. I had the speed sensor electronics fail on my NC30, so just because the sensor is plugged in does not mean the cdi is getting the ok to rev signal. You can use a resistor to bypass the sensor and fool the cdi. If you cannot find on this site I have a copy of the document somewhere.

[magg]

Another thought, if it does not run cleanly to 5000 rpm and it appears to have lost two cylinders maybe one of the ignition pickups has failed. Not sure how the tacho signal is derived but a lost pickup may also result in lost tacho signal.

[Mattzmad]

Ok cheers magg. Ill attempt to get my hands on a working cdi 1st and go from there.

[Mattzmad]

Just got an hrc copy cdi unit through. Pluged it in and bike runs a dream. Revs right out but the tacho still says no.