NC23 easy start, cuts out, won't start again

[skinnybwoy]

Hi guys

OK before I start let me just say that I have been reading through this forum for the last half hour but can't seem to find any posts exactly like my problem. so here goes, hope someone can help.

I've just taken delivery of my new bike, a CBR400 NC23. Unfortunately, it's got a few gremlins that need sorting out.
The previous owner had it standing for a while, a few months. I took it out for a test ride, pretty short one, maybe 2km, and it seemed to run really nicely. It cut out as I pulled back into his place, but I thought I'd stalled it. It did start up again so it didn't seem to be anything to worry about.

Now today, on the ride home, when I picked it up it started first thumb of the button, idled nice and smoothly, and went just fine for the first 4 or 5km. After that, when pulling up to a traffic light, as I stopped, it just cut out. It refused to start at all. Luckily my brother was behind me so we took it down a side street and bump started it. It ran fine for another kilometer, then, same thing. cut out at a traffic light. This time, no amount of pushing would get it started. I pushed it home (by this stage we were fairly close). Got to my street after about 10 minutes of pushing, gave it a bump, and it fired up fine.

I left to stand for an hour, thumbed the starter, no problem, fired up quickly and idled smoothly.

The previous owner had the engine rebuilt, the only fault I've been able to find is that the radiator was damaged before and fixed with steel putty.

Any ideas?

[veefer400]

My first thoughts - fuel starvation.

Hence it will start when left for more fuel to seep down thro to the carbs...

Is it an Aero (jellymould) or later NC23?

I take it there is plenty of fuel in the tank...

Have you tried running it on reserve anyway?

[Wozza]

As the bike is new to you, and it's been standing for a while, I would strip and clean the carbs (checking all settings and jet sizes), check/replace the spark plugs and give it new oil and a filter. I would do this as a matter of principle regardless of any problems encountered, so that you know the carbs are setup correctly and you know when you next need to replace the oil/filter/spark plugs. As a side effect this may solve your problem - if not you can cross off the carbs on your list of things to check.

[skinnybwoy]

veefer, it's a later NC23, not the jellymould.

wozza, I am definitely gonna get on the oil change, it'll have to be on monday though when the bike shops open.

Fuel starvation, possibly... There is fuel in the tank and I was running it on reserve. do you guys think it could be old fuel that might have gummed up the carbs? It did seem to rev cleanly but started to hesitate just before it cut out.

What could be causing the fuel starvation?

[RockerTed]

i would also check the battery, the nc23,s are very prone to bad running if the battery is not fully charged. my last one was as you described yours, and it was the reg/rec and duff battery,ted

[Wozza]

Now you say that Ted, I remember mine was very easy to stall when the battery was dead.

Fuel starvation - check the fuel filter, check the tap is flowing properly. Check the tank isn't full of gunk at the bottom. Unlikely, but check the tank cap is breathing air properly.

In fact, empty and flush the tank out - I would add this to my list of things to do 'on principle'.

[skinnybwoy]

Thanks so much for the replies guys. This forum rocks

I had a CBR600 a while back that gave me endless problems, one of which was a faulty fuel pump, which caused fuel starvation issues. But that was different to how this one is responding. With my 600's fuel issue, when the pump would fail, it was usually while I was cruising (once at 170kph on the freeway, not fun) it would just hit a brick wall, refuse to rev then kinda drone to a stop.

With the NC23, it revs fine, there's no cutting while it's running. Only, as soon as I stop and dip the clutch, it seems to stall immediately and won't restart. So perhaps it's not fuel starvation.

I'll drain the tank and get some new fuel and check the fuel lines. I'll charge the battery overnight too.

How do I check to see if the reg/rec is faulty?

[veefer400]

Thanks so much for the replies guys. This forum rocks

I had a CBR600 a while back that gave me endless problems, one of which was a faulty fuel pump, which caused fuel starvation issues. But that was different to how this one is responding. With my 600's fuel issue, when the pump would fail, it was usually while I was cruising (once at 170kph on the freeway, not fun) it would just hit a brick wall, refuse to rev then kinda drone to a stop.

With the NC23, it revs fine, there's no cutting while it's running. Only, as soon as I stop and dip the clutch, it seems to stall immediately and won't restart. So perhaps it's not fuel starvation.

I'll drain the tank and get some new fuel and check the fuel lines. I'll charge the battery overnight too.

How do I check to see if the reg/rec is faulty?

Reg/rectifiers are a nightmare on the '23... My mates reg/rect went and boiled his battery!

I would imagine a simple multimeter test over the + & - when the battery is running would let you know? They are cheap enough from DSS (davidsilverspares.co.uk) anyways...

[skinnybwoy]

Ok, I'm pretty sure the culprit is the reg/rec unit. I charged the battery for a good 30 hours or so, it still says only half-charged on the tester. I think a bad reg/rec cooked the battery. This, combined with the symptoms I described, as well as the burned-out tacho (guessing), in conjunction with some internet research about symptoms of a bad reg/rec, leads me to that conclusion.

I've got a new battery and a new regulator rectifier is on its way. Let's see if this works...

[skinnybwoy]

Ok I've fitted a brand new reg/rec and brand new battery. Took the bike out for a half hour spin around the suburbs and, touch wood, no more issues...