carby problem

[timmyrocks]

hey guys this a question about my vfr400 not technical so dun worry,
at idle it only runs on 3 cylinders, but when on the throttle its runs on 4 so i think the pilot jet is blocked (when i brought it it was running on 4) so i wouldnt think its out or sync, or mixture screws are out?
now should i leave it as it starts, runs, revs, rides smooth as and just hope it clears itself and for the timebeing just use the throttle at idle (being a race bike that wont be a problem cause it wont be idleing for to long
or HTFU and strip and clean and hope i dont muk them up???

my dads saying is while its working leave it!!!! so im a bit unshure
HELP!!! cheers Tim

[mike-s]

If you dont need the idle, then yeah, you can leave it running on three if you really want, but if you do a big rolloff to zero on a down change then you never know, you could have it stall. I would suggest that at first put a half bottle of carby cleaner in the tank, turn the idle jet out a half turn richer on the problematic idle circuit and run it through, then put the other half of the bottle in and refuel it again.

If that doesn't help (the point of richening it up is to help any flow of fuel through the circuit at all, assuming the idle circuit is set correctly as well as the balance) then it may as well just pay for you to remove the carbs and soak them in carby cleaner for a few hours (i left them for 3 days sealed in a jar of cleaner) before using fishing line to clean crap out of them. That combined with using an old toothbrush were the only ways i could get my carbs clean enough to run.

All that being said the only way to make sure is to do them all from top to bottom, strip the carbs out, clean the bodies out, clean the jets out, clean the emulsion tubes out (trust me about those, mine were GREEN with shit caked in them), reassemble and balance them.

[Rusty]

CV carbs are pretty simple things. Getting 'em off and on again will be the most difficult part of the exercise.

You'd probably find that just cleaning the emulsion tubes out would fix it, though while it's all apart it's a good opportunity to clean properly. Just make sure everything goes back where it came from and be gentle with the floats.

Run a tank of E10 through it every now and then.

[timmyrocks]

yer i have chucked some injector cleaner in the tank and some metho to clean it up, its just that when i brought the bike (bout 3-4 weeks ago) was running on all four so i think just a bit of shit has got in there so i am hopin after a good thrash at a track day it clears up with the injector cleaner and that.
if not i will give them a strip and clean
and for my first track day i will just be on the throttle and wont let it idle hehe and try not to do a big roll off haha
cheers Tim

[IsleofNinja]

Or there could be an air leak between the carb and the head ie hose from carb to fuel tap , manifold not seated properly , clamp loose etc............

[timmyrocks]

i have checked all clamps and hoses and they appear to be connected properly and the fuel tap has been modified by the HRC manual to not rely on vaccum from the engine to open the valve so it doesnt starve of fuel as these are common for this at the track so i have heard cheers guys will keep yars posted with how i go
cheers Tim

[Rusty]

... the fuel tap has been modified by the HRC manual to not rely on vaccum from the engine to open the valve so it doesnt starve of fuel as these are common for this at the track so i have heard ...

I'd forgotten about that. My old 500 had the same problem when I first got it. I took the diaphragm out and soldered up the vacuum port on the tap. Problem fixed.

[IsleofNinja]

How did she go Tim??

[timmyrocks]

i removed the carbies today and reset the float levels as these were slightly out, i removed the jets and found a few had some gunk in them so i cleared them and used fishing wire and a hose to blow through the fuel passages to make shore they were free.
i then fitted the carbs and tried again but still ran on 3 and i could hear it firing on the 4th every now and then so i removed the carbs again checked the idle jet of the cylinder not firing, it was free, so i then richened up the mixture by turning the pilot screws 1/2 a turn out and VROOM, V4 sound purring outa da exhaust sounds beaut still havent had it fully warmed up yet as by this time it was getting late so i am happy with my progress and packed up, will start it tommorro and make shore shes all good when its warm
cheers will keep yars posted
Tim