Idling problem

[KoreaRVF]

Hello all, I have a NC35 and I'm having issues with the idle.
When I start the bike up and getting it going without the choke the bike idles fine. After getting fully warmed up the idling begins to become erratic. When the engine is hot, for example when I'm sitting in traffic, the engine cuts off. It starts up fine again right away and there are no problems with the bike when the engine is being revved. Had the carbs off cleaned and float levels checked, new sparks, checked the spark plug cables and new air filter less than a few thousand clicks ago. New reg/rec, battery at the same time too and the charging system has been throughly checked. I'm at a loss. The only thing that I can think of (on this site while I was digging around looking for information on this problem) is that the NC30s suffered from issues with old fuel lines collapsing when they get hot. Has anyone else experienced any similiar issues with their NC35?

Thanks in advance!

[Cammo]

The only thing that I can think of (on this site while I was digging around looking for information on this problem) is that the NC30s suffered from issues with old fuel lines collapsing when they get hot.

It's the fuel tap air vacuum line, not a fuel line. This air opens the fuel tap to allow fuel through to the carbs. When it gets old it can collapse when warm, stopping fuel getting to the carbs. This problem will affect rvf's too, not just nc30's. It's worth replacing this hose if you have any doubts about it causing a problem, it's not always easy to tell whether it's at fault. The hose runs from beneath the right rear carb to the bottom of the fuel tap.

However, if the engine starts up again straight away I doubt the carbs are running out of fuel.

Does the bike cut out because the idle fluctuates too low? What rpm is the idle fluctuating to and from?

A fluctuating idle is usually a sign that the carbs need to be synchronised/balanced.

[CMSMJ1]

How far do you get before the bike starts to play up? Are you saying that once it dies, then to get it going again, you have to keep some revs up?

WHat was the charging system fault? Was the alternator checked? If you are getting the fuel and it fires back up again then I am not entirely convinced it is a fuel fault.

If you can check charging again as it could be a partially knackered alternator - battery drives oyu with some charge for a 20 min or so...then as it starts to fade it will not hold idle. rest it a touch, lots of revs to keep the partial charging going and off you go..

Or not..lol, give us some more info

[KoreaRVF]

Thanks for the replies guys. I haven't had enough time to play around with the bike this weekend but I will try to get some work done in the evenings this week. I'll let you know if I find anything else wrong with it.

[KoreaRVF]

I got the bike out today and decided to go back over the charging system once more as you lads had suggested.
I checked the battery which gave me a normal reading, then I checked the battery terminals again at 5500rpm everything checked out normal there too. Then I went on and looked at the three yellow wires coming from the alternator. The resistance on these all checked out fine.

As for more information on the idle issue I can tell you that right after getting warmed up the bike will idle at around 1200-/+ 100 then the idle becomes irratic after about 15mins of driving especially when the temperature gauge begins to creep up. It will go as high as 1500 then splutter fluctuate between 1400 to 1000 then cut off.

[uber pikey]

I know you have already checked the charging system but did you check it from cold starting? The problem you might have is that the charging system might be breaking down when hot, this might be worth checking again when hot just to eliminate the cause.

[265chemic]

Im having this same problem and havent been able to diagnose it yet.. Im thinking possibly carb piston flutcuations, as sometimes coming off the throttle gently it sits at 2k, whereas if you snap it it settles back down to 1700