Lumpy idle NC30

[Stoozak]

(Dual post from the jetting sticky)

Alright so I removed carbs, 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

[Icemaestro]

Mine does that sometimes, I feel like it depends on the bike temperature? I forgot to check the float heights, so was hoping it was that...like you I had mine balanced before rejetting

[Neosophist]

Sometimes wrong if its cutting out.

Your vaccum pipe ok? it could be running out of fuel if the pipe is leaking.

After adjusting the carbs (dont forget vavle clearances) you need to balance the carbs with vaccm gagues.


It should idle super smooth all day long

[Stoozak]

Ok balanced the carbs using the drill bit method and it's much much better. No more lumpy idle. It is a little slow returning to idle but it might be my imagination, I'll take a video tomorrow for some opinions.

Out of interest is it possible to get to the pilot screws with the carbs on?

[Stoozak]

Right, this is her at warm at idle. Heaps better than before.

http://youtu.be/okjrTdG8fvI

Your opinions on the rev drop off rate?

[vfrman]

Yep. It sounds a little slow to me. I can't remember what causes this, so I don't want to send you on a goose chase. Is the throttle free and are the cables not tight (if that makes sense)?

[Stoozak]

They seem to be. Is there an easy way to lube the cables from the top?

[Neosophist]

Revs hanging around 2000 rpm before it reutns to idle is classic sign of "lean condition"

do you have an airleak anywhere, most common is carbs not sealing in the rubbers themselves or the rubbers being knackered.

Spray something flammable like brake cleaner / easy start aroudn the carb rubbers when backing off the throttle, if it returns to idle quicker then you have a leak somewhere.

[Stoozak]

Okie dokie, I'll replace the rubbers just to be safe.

Is there anything else I should be looking for or setting while I have the carbs off?

[Stoozak]

Ok so i sprayed all the rubbers and didnt get much reaction.

I took the carbs off and did find that the vacuum take off for the fuel tap wasnt tightened enough.

Anyway, I tightened it up, greased the rubbers and did it all back up. I also adjusted the pilot screws out a quarter turn.

It seems to be better, but it might be in my head!

http://youtu.be/Ss4eHS9UQmA