NC23 clicking noise below 4000RPM misfire

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willpisme
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NC23 clicking noise below 4000RPM misfire

Post by willpisme » Thu Sep 20, 2012 8:56 am

Hi all,

Sorted the overall misfire out on my nc23 by replacing a HT lead (there was nothing at the end going into the coil!) But now when the engine is up to temperature it will not idle or pull at revs under 4000RPM very well. This can be very annoying when in slow moving traffic as the stall factor is extremely high! It kind of sounds like its running on 2/3 cylinders when it does this.
Once it gets above 4000 it clears and runs perfect.
When below 4000 and up to temperature there is a clicking noise and the temperature gauge moves up and down erratically.

I have a gold CDI and all standard apart from that.


Thanks for any advice!

Ollie7195
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Re: NC23 clicking noise below 4000RPM misfire

Post by Ollie7195 » Sun Nov 13, 2022 6:58 pm

Hi did you ever get anywhere with this? I’ve got a NC29 that was running a bit rough, then after a while it started to drop to what sounds like 2 cylinders and needs to rev past 6k before they come back in, I’ve cleaned and rebuilt the carbs twice, replaced the spark plugs checked the ht leads, replaced one of the coils and interchanged them with absolutely no change, beginning to wonder if it’s a faulty cdi?

MadMotoUK
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Re: NC23 clicking noise below 4000RPM misfire

Post by MadMotoUK » Sun Nov 13, 2022 9:16 pm

What condition are the plugs in? Are they gapped correctly? Try closing the plug gap by a few thou and see if the situation improves, if it does then it's down to a weak spark. A weak spark could be down to a failing CDI or it could be something simple like you're not getting a steady 12v to the coil.

Also worth checking the coil resistance on the primary and secondary sides, tolerances are in the Honda manual or Haynes manual.

magg
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Re: NC23 clicking noise below 4000RPM misfire

Post by magg » Mon Nov 14, 2022 4:22 am

An erratic reading temp gauge suggests an electrical problem. As MadMotoUK suggested, check that battery voltage at the TIC unit etc, also check the wiring loom chassis connection. A faulty loom/chassis connection can result in weird instrument and running effects.

I make the same suggestion to Ollie7195.

Ollie7195
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Re: NC23 clicking noise below 4000RPM misfire

Post by Ollie7195 » Mon Nov 14, 2022 6:20 pm

MadMotoUK wrote:
Sun Nov 13, 2022 9:16 pm
What condition are the plugs in? Are they gapped correctly? Try closing the plug gap by a few thou and see if the situation improves, if it does then it's down to a weak spark. A weak spark could be down to a failing CDI or it could be something simple like you're not getting a steady 12v to the coil.

Also worth checking the coil resistance on the primary and secondary sides, tolerances are in the Honda manual or Haynes manual.
Plugs are brand new (changed since having the issue) have checked ht leads, checked and replaced coils but no difference

Any idea what the voltage from the speed limiter should be? As I’ve been getting 10.4V at the CDI but not sure what it needs to be a good reading?

magg
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Re: NC23 clicking noise below 4000RPM misfire

Post by magg » Mon Nov 14, 2022 7:42 pm

Atre you actually measuring the speed limiter signal or power to the TCI unit, don't believe NC23 uses CDI. Either way something closer to full battery voltage would be expected, not 10.4 volts. Battery voltage should be more than 13 volts engine off or running. Any less is dud stator, rect/reg, battery and/or wiring.

Ollie7195
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Re: NC23 clicking noise below 4000RPM misfire

Post by Ollie7195 » Mon Nov 14, 2022 7:57 pm

I’m measuring the limiter signal at the plug for the CDI (TCI) which ever it is, with the CDI disconnected, it’s a NC29 I have no idea how to identify if it’s a CDI or TCI?

I measured it with the charger on so battery voltage was 13.1V and I was still only getting 10.6V

I’ve given the connectors a good wiggle at the speedo end and no change observed

I also put a led volt display between earth and the speed limiter signal and it dragged the voltage down to 5V, being a low current device I’m surprised by this and suspecting something might be wrong with the limiter circuit?

Rec/reg is all ok and charges fine when the bike is running

MadMotoUK
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Re: NC23 clicking noise below 4000RPM misfire

Post by MadMotoUK » Mon Nov 14, 2022 8:53 pm

The most reliable place to test for coil input voltage is at the spade terminal on the coil itself. Just pull the connector back a few mm and place the probe on the terminal, other probe to earth. One side should give 12v-14v the other should read zero.

magg
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Re: NC23 clicking noise below 4000RPM misfire

Post by magg » Mon Nov 14, 2022 8:58 pm

You can bypass the speed limiter circuit by disconnecting the plug at the speedo and connecting a 2000 ohm resistor between blue/yellow and black/brown wires of the loom plug. Simply disconnecting the plug at the speedo will be detected by the TCI as a fault at startup and will stop engine from running beyond 5000rpm. The documents section on the home page of this site contains this info.

CB1pod70
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Re: NC23 clicking noise below 4000RPM misfire

Post by CB1pod70 » Wed Nov 23, 2022 9:55 am

I know you've cleaned the carbs twice but I can almost guarantee that the problem is your slow jets. Above 6000 rpm the carbs are running on the main jets and below that the slow jets. New ones aren't that expensive - I have them in stock @ GF Racing for £24.00 + p&p if you want to give me a call on 07522 166832. Don't be tempted by the Chinese ones on Ebay etc. - they are dog shite.......

If it was a problem with the CDI, it would affect the bike across the entire rev range although bypassing the speed limiter at the CDI end will eliminate any issues with dodgy wiring and enable you to eliminate that as a possible issue.


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