Think I may have located the problem

I removed the speedometer, stipped out the speed limiter unit and fitted it in a plastic box. This is cable tied to the clock bracket inside the fairing, and I was hoping it would bypass the speed restriction. I also had a secondhand black box de-restrictor spare, and thought I would try it last night. The bike now revs far better so I'm wondering if my DIY bypass put the ignition unit into limp mode? Anyway I'll leave the black box unit installed for the track day, and worry about carb needle washers later. I don't think the NC3o has washers as standard, but the RVF does according to haynes manual.

It may well have cut the spark to two cylinders if it was a restriction issue. It's certainly not easy to tell when spark is cut over 5000 rpm to 2 cylinders when revving it in neutral.

GeeTee wrote: I don't think the NC3o has washers as standard, but the RVF does according to haynes manual.

Both have a single washer as standard. Leaving them out 'shouldn't' be too much of an issue on the track, but some nc30's are more particular than others.

Alright so I removed carb, added washers and placed the needles in the correct positions (they were backwards), drilled the 2.5mm hole, rejetted to 118/120, and turned idle screws out 2.25 turns.

The bike goes like a rocket and the flat spot is gone, but I have a lumpy idle.

Occasionally it will be so lumpy that the revs drop until it cuts out completely.

Any ideas?

Vfr400 lumpy idle: http://youtu.be/NHws1-fboZo

Carb balance?

Hmm, they were balance right before I rejetted them. So i was hoping to get away with not doing it again.

Could it be that simple?

Could be. Could also be an air leak somewhere.

Cheers for that, did it yesterday and made a noticeable difference - especially drilling out the slides. Recommend it to all owners!!

Hi all, Could anyone offer any advise on this? : http://youtu.be/qJx2dINOsXE (apart from 'dont crank the shit out of it when it obviously doesnt want to go', That was definitely stupid of me) Its an NC35, and the times when it did fire i was feathering the throttle open quite wide just to keep it alive.

The bike has not run in a long time and after the video was taken i removed the carbs to gut em and clean them, but have not done that yet. Might consider upping the jets in them also, depending on whats in there. The bike has a twin stack yammamoto exhaust, standard intake.

Thanks.

Thanks for this. Much clearer than the Haynes manual. This is my Good Friday job!

Hi, After 3 years of owning the bike, I've finally undertaken this carb guide.

Firstly Ive only done this just out of curiosity , the bike ran fine apart from a tiny midrange flat spot, it also idled and started perfectly. I had an idea I maybe should rejet when I put a different system on.

Anyway I opened them all up and found the main jets were hexagonal at the top and the size was written on the top , removed with a 6mm socket, any idea what manufacturer makes these. Inside it was perfectly clean as well.

But the jets seemed odd at the front they were 117 and at the rear they were 115 , so different to what everyone else has , also the pilot screws were all 3 and half turns out. Now I've followed this guide and turned them 2 and 1/4 out.

Anyway ill be changing the jets to those written in this guide 120/122, just thought id let you know what I found and also can anyone shed some light on my current jets.

PS now I think about it does explain the discolouration of my rear exhaust downpipes (rainbow effect) must have been getting too hot from the jetting? maybe should have realised this sooner

Sam

PS This guide is brilliant BTW