Rewiring an NC21

[Chrissy_J]

I'm currently rewiring my NC21, since the original loom was scrapped because everyone and his dog had been fiddling with it... it's only using the essentials 'cos I'm not running lights.

Right now I'm connecting everything up but have hit a couple of snags:

The NC21 has four coils, one per cylinder. Each coil has two primary winding terminals, one with a green base and one black. Which one is the positive terminal, or doesn't it matter so long as I keep it consistent (eg. make all green tags the +ve) ?

Also... the reg/rec on the NC21 has seven wires; three yellow, two green and two red/white. I know the yellow wires are to the alternator and the green wires are to earth, which means that one of the red/white wires must supply the battery. What does the other wire go to, if anything?

Thanks for your help!

[Neosophist]

Hiya!

I have a spare NC2x loom if you want it. I'm pretty certain its an NC21 loom but i'll double check.. if its a 24 you'll just need to change a few plugs.

Are you using a different Reg/Rec?

The Reds are connected together, same for the greens. Yellows can go either-way around.

When I switched an an R6 reg/rec I soldered them together.. it just splits to load better with two wires.

As for the coils, this is a tricky one.. It doesn't matter per-se.. but you technically get a 'better' spark if there wired the right way around.

You only have to find out which wire is positive and use that on the positive of the coil (not green tag) On the original loom they all have number tags on them (probably long gone by now)

I should have an NC21 wiring diagram I can cross reference the wires colours and let you know which ones are + / -.

How much spare cash do you have knocking around?

You could get some CBR1000RR / CBR600RR Stick coils and loom and do away with your coils and ignition leads.

You'll need 4 balast resistors to bring the resitance back in check (I paid £3.00 each for 0.8ohm ignition balasts) that I have connected to the frame.

Results are less wires / more space / better spark / smoother running.

[Chrissy_J]

Thanks for your input!

The original loom was a bit of a wreck, all Scotchloks and speaker wires... the original solenoid had it's fuse, well, fused together in a short, and no matching HT leads... Gods only know how it ever run!

But run it did, so I have no reason to doubt the original equipment... yes, the reg/rec is the original, it sits under the seat and it doesn't have any cooling fins... should I be worried? In fact should I be thinking about replacing it with a newer model?

The coils are original too, they have no markings on (in fact the only thing that was marked was the one original HT lead on #3) but I'll try what you suggested.

From searching the forum I've heard about these stick coils... I don't know much about them but they seem a good idea. At the moment I'm almost broke, though ... I'll get the bike running first, then I can think about improving the sparks. I can include it in with the costs of getting it upjetted and Dyno'd, etc.

I should have an NC21 wiring diagram I can cross reference the wires colours and let you know which ones are + / -

That would be very kind, thank you!

[Chrissy_J]

Actually, having thought about it, the stick coils seem A Good Idea... since I have to get new plug caps and HT leads anyway, it's probably a better option to get some packs and loom from a CBR600RR instead.

Thanks for the tip!

[Cammo]

the reg/rec is the original, it sits under the seat and it doesn't have any cooling fins... should I be worried? In fact should I be thinking about replacing it with a newer model?

Always a good idea on most older honda bikes!

Honda reg/recs have left me stranded more than once...!!