running problem tech help needed asap

[eugene0174]

hi guy im a newbie here and i have not long brought a cbr400 nc23 1989 just had after market fairing and exhaust put on her, but ive now got a problem with her.
she starts and runs and able to ride but after about 1/2mins she dies a death and i had to wait 30mins before she'd start again then same thing happened, shes at the local bike garage as i took her there be see if it was a quick fit but there stumped they said theyve check fuel pipes, air filter, carbs etc and there all fine they think it could be the cdi unit but if it was the cdi she wouldnt start right??? any help please needed asap
forgot to say when 1st happened been riding for about an hour then oil light came on and see died within seconds of it coming on oil is ok been checked

[dunkenb]

When you say wont start is it still turning over and dash lights still on?

[eugene0174]

they go off but then come back on and yes it sparks n turns over

[gullarm]

You need to go back to square one.

Does it run on tickover then conk out or only when riding around?

Is the fuel getting thru when it conks out? Are the float bowls still full. You would more likely feel a mis fire just before it goes. It will run for ages on tickover with no fuel feed to the carbs - a good 10 mins or so.

After that its a case of check all the things you can - and by pass them if poss.
Remove fuel filter, by pass the fuel pump ( does the nc 23 does have one? )
Can you bump start it back to life?
Is the batt ok, fully charged.
Is it charging, over 14 odd volts at 5000rpm
Is it wet when you were riding - electric and water dont like each other
Are the fuses in tight - corroded contacts
Air lock in fuel tank, try riding with the cap open


Do one thing at a time - and try and repeat the fault over and over again so you can tell when it will fail or not

read my post it may help

viewtopic.php?f=28&t=35200

Above all when you fix it LET US KNOW so we can fix it when it happens to other bikes.

[eugene0174]

garage says theyve done all this yes was running for ages on tick over now only for a few mins, wont bump start gotta leave her for about 30mins before she'll fire up again

[CMSMJ1]

not getting fuel is it...?

[gullarm]

Like I say - if it starts every 30 mins you could work out where the fault lies.

I wouldn't believe a word a garage say. On my newish car I had 2 bald tyres ( they were only 3 months old!!! ), cracked anti roll bar ( it had moved to the left 10mm!! and was knocking the suspension arm ) to name a few. Con artisits the lot of them. Unless you find a good un and they are rare.

Bypass the fuel element - easy job. No filter/no pump/ cap open/also elimates fuel pump relay.

Wrong fuel tap? I fitted a 50cc fuel tap to a 125CC, guess what it ran for 10-15 mins then cut out. Started straight away. Repeat.................

Keep checking there is fuel in the float bowls when it stops.

And does it splutter to a stop or just stop dead.

And what revs is it ticking over at?


Try the pick up coil ( or pulse generator as it can be called ) - the one in the engine in the left hand side cover. Not the 2 ignition coils on top of the engine.

Get a DVM set to Ohms range and take a reading. It should be 340 - 420 ohms.

I hard wired my DVM into the coil so could check it when I wanted ( ignition off of course before checking ).

It read fine when cool ( think 450 ohms ) then went open circuit when hot, but not when riding around. Only after sitting for a few mins after riding with the enigine off.


Get your hands dirty.

[eugene0174]

Cheers for the help guys I'll try and I'll get back and let you all know

[Davez29]

Fuel starvation (vacuum) due to a blocked tank breather? oops just noticed it was mentioned above..

[eugene0174]

bikes working fine ty for the help everyone only 1 problem now the fuel pump has a major leak cant be fix once again after garage fixed it looks like they tampered with it so after a new fuel pump asap unless it can be bypassed some how and for the bike to keep running and working fine