NC23 Won't Rev, help needed please!

[thunderace]

I'm pretty sure I've played up against that bike in F400. It's a cracker and was lots quicker than my completely bog standard FZ400R was.

Do as others have suggested, get a track day booked. Leave it idling for ten minutes before you take it out, a few gentle sighting laps then go to town and report back. I think you'll find that any issues should be sorted out after a good thrashing

[Geoff 3xv]

Hi Guys,

I have been helping Howard with his NC23 and it's been puzzling me too. Our friend Ron has a zxr400 that is set up nicely and after a few minutes of running that revs cleanly in neutral with no hesitation or rough running. We were convinced that the NC23 should be very similar. In the past I myself have owned a FZR400RSP and a NC29. Both of those ran lovely in neutral too.

Obviously the fact that Howard is unable to take his bike up the road for a test ride isn't helping us from getting to the bottom of the problem. I agree it needs to be ridden to see how it responds under load.

I'll add to Howards description of the problem:

Part throttle fuelling is spot on. Anything upto quarter throttle is perfect. It idles flawlessly and revs cleanly at part throttle upto 7k (obviously once the bike has had chance to warm up). The problems come when it is fuelling on the main jet circuit.

When I first heard the bike running I was convinced that the main jets were too small as it was exhibiting traits of an engine starved of fuel and i'd seen it before with my other 400's when aftermarket exhausts had been fitted without the bike being jetted up accordingly.

We had a set of aftermarket 125 main jets and tried those to no avail. Interestingly we taped up the two front intakes to the airbox allowing the engine only to breathe through the 2 small holes in the top of the airbox and the engine running drastically improved upto 10k. Obviously endlessly revving the bike up in neutral isn't the way to go but it's it we had to go on sadly.

The previous owner has changed the electrics somewhat in the past, the bike isn't running total loss but the previous owner did say " it is running a crude trickle charge system " so I'm wondering if there is an issue here. I have told Howard to source a standard NC23 loom to return it to stock and see if it improves the situation. Looms are cheap and there are plenty around so figured it was an easy thing to do. Plus Howard wants the battery to be charging properly so that he doesn't have battery issues on a trackday.

Can anyone enlighten us on the resistor mod? I'm guessing the bike will have already had this done but it would be good to know what is involved.

Cheers,

Geoff

[Cammo]

I have been helping Howard with his NC23 and it's been puzzling me too. Our friend Ron has a zxr400 that is set up nicely and after a few minutes of running that revs cleanly in neutral with no hesitation or rough running. We were convinced that the NC23 should be very similar. Geoff

I disagree. There are many factors (carb setup, ramair etc) that will stop it revving to redline in neutral but fine under load.

" it is running a crude trickle charge system " so I'm wondering if there is an issue here. I have told Howard to source a standard NC23 loom to return it to stock and see if it improves the situation.

It doesn't sound to me like the owner was referring to the bike's charging circuit, rather a point at which to connect an electrical trickle charger to charge the bike's battery?

Forget changing the loom, totally pointless until you identify an issue. Just do a battery voltage test at revs, if there's an issue then look elsewhere.

[Geoff 3xv]

Thanks, we will give that a go.

Regarding the trickle charge. No its not that, the bloke said he changed the electrics so that it is almost total loss but the generator still puts a little bit of charge into the battery. He said he did it so that the generator didn't use too much of the engines power. The bike still has the reg/rec fitted but all the wiring to it is custom and not stock. Hence my suggestion of fitting a stock loom so the battery is charging properly as it was designed to do.

Cheers,

Geoff

[CMSMJ1]

The bike will still run and work perfectly if you disconnect the reg rec. SO I doubt that is the issue. Unless the battery itself is too small and weak to run the bike unles it is getting a charge.

is it running a std battery and is that healthy? Might be as simple as the bike not having enough electrical power to sustain high revs...and you think it is all good as it has a generator..that is shit!

[Geoff 3xv]

is it running a std battery and is that healthy? Might be as simple as the bike not having enough electrical power to sustain high revs...and you think it is all good as it has a generator..that is shit!

What I meant was by fitting a stock loom the wiring is connected as Mr Honda intended so we have eliminated the previous owners tampered wiring if that makes sense?

I agree that the generator still might not charge the battery but as I don't know/understand what the previous owner has done to the wiring I figured it best to return it to the stock set up. Am I talking sense?

Is the CDI a high voltage CDI on the NC23 or is it DC-DC?

I'm assuming DC-DC. Is that correct?

Cheers,

Geoff

[CMSMJ1]

Hey Geoff - the generator mate!

It seems like the bike has not go the beans to be able to run itself and it is stuck in the no mans land between total loss and fully charging.

I'd get a jump lead onto it from another bike to provide additional juice and see if it revs better then..simple test and an easy fix.

cheers!

[Geoff 3xv]

The jump lead idea is a great idea!

Thanks very much.

Geoff