bricheun
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 posted on 5/2/07 at 07:13 AM |
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Carbs not returning - not return spring problem..
My ZX6R carbs are running great one off idle position, however, it will never return to idle without a blip of the throttle.
It is found that carb 1 which has the throttle cable does return to idle however carbs 2,3,4 does not. It requires a push with a screwdriver before
everything returns to normal.
It seems 1 effect 2,3,4, 2 effects 3,4 etc, therefore I cannot tune it properly.
I sprayed WD40 on the linkages and roller bearings without improvement..
Does anyone know how to fix this problem? It very hairy driving it now because off throttle sometimes hang at 3000rpm!!
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bricheun
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| posted on 5/2/07 at 10:14 AM |
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Thanks for the advice. I have balanced using the drill bit method. I slid the bit in felt the same resistance. If I turn the throttle by hand sure it
lines up because the closing is more abrupt.
In real life situation when you are driving you very rarely drive with on/off abrupt more like an ease off the throttle.
So, carb#1 closed, carb#2 slighty not closed i.e. 0.2mm, carb#3 because carb#2 is out is also 0.2mm+0.2mm, carb#4 is 0.2+0.2+0.2...hence the high
idle. On snap close throttle or blipping the throttle the butterflies are all closed evenly.
If I ease off the throttle by hand or cable it does hang up, this is the only situation it happens. I am thinking maybe the spring (tiny one) which
goes into where the sync screw goes might be too weak to put enough pressure during the return process.
Now I know why newer bikes use the middle to throttle rather than the far end one.
Middle one turns only 2 carbs, where as now, 1 carb turn all 4 carbs.
I tried to tune it so that it drops rpm quickly on slow throttle release but this makes it go "chug chug chug" on idle and off throttle
meaning the sync is out..the idea was on slow throttle return the butterflies are artificially stanggered so that all close up. But..on throttle
up..they are out of sync.
I will try to sync it again and maybe add stronger little springs to see if it improves the situation...
[Edited on 5/2/07 by bricheun]
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Surrey Dave
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| posted on 5/2/07 at 11:58 AM |
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Return Cable
The throttle balance is important , but also on a bike most carbs have a return or closing cable.
Not normally fitted in the car setup ,so you are just relying on the weedy spring on the throttle shaft.
A lot of people add an extra return spring , i have not and my throttle sometimes hangs a little, can be v.irritating.
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mark chandler
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| posted on 5/2/07 at 01:12 PM |
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But you have to be careful, a big spring will bend the spindles.
If you have a sticking throttle now have you twisted one of the spindles while setting up with a drill ?
Much better to use a manometer or simple listen to the hiss, surprising how good a method this is.
Regards Mark
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Phil.J
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| posted on 5/2/07 at 01:43 PM |
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Have you checked the cable is free in the outer sleeve, or is not kinked or pinched anywhere? A stray wire whisker from the inner cable can also cause
sticking.
ATB
Phil
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bricheun
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| posted on 5/2/07 at 04:00 PM |
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Took out and retied
Thanks for the support..I tried to suss it out again with the carbs out of the car. Checked all the springs and replaced the little spring with a
slightly stronger one from another carb.
The drill bit method did not bend the spindle because I did not rest the butterflies on the drill bit, just eased it in with a slight drag (drill bit
using the smooth end :-) )
Another thing I noticed was the main spring was 1 notch off, so I moved it over to where it should be. Now the movement is better. When the throttle
is moved by hand gently on/off idle it now returns to "zero" position resting on the idle stop screw.
The force from the main spring helped a bit, but driving it around still had a little idle hanging..not so serious but gently dropping..slowly from
2000rpm to 1000rpm in around 10 seconds.
 
Rescued attachment P1000772.JPG
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jacko
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| posted on 5/2/07 at 05:41 PM |
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Hi when i first fitted my zx9r carbs i had the same problem i found it was the rubber manifold pipe that was rubbing on the springs that are in your
photo . + you need a second return spring fitted
Jacko
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bricheun
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| posted on 6/2/07 at 01:56 AM |
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Ok, I will check it out again later on to see if the rubber hose is rubbing against it.
I will try to make a return spring adaptor on the side..
cheers..
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snapper
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| posted on 6/2/07 at 06:27 PM |
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I am also considering a light return spring on the throttle pedal, this should keep the cable lightly loaded.
Well oiled or teflon coated inner cable.
already have an extra spring acting on the second carb. The cable acts on carb 2 almost in the middle of the four.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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bricheun
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| posted on 8/2/07 at 07:17 AM |
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The bit where the silicone tubes attach on the carbs are very short on the ZX6R carbs, if I move them out a little, it slips off too easily when I am
driving.
The tube supplied by Boggs is really thick and squidgy when you tighten up the hose clamps. If I push the carbs in, then yes it snags on the
springs.
I was driving along nicely when suddenly it was running very rough until the engine cut out. Checked and the carbs were hanging off!...
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kurt t
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| posted on 16/2/07 at 07:39 AM |
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I feel your pain
I allso have the same problem, I am running the yamaha r1 carbs. they have the throttle linkage up one end of the 4 carbs . Same as you explained no 1
carby that has the mouse trap spring mounted to it returns nice but no 2,3 and 4 get less and less spring pressure.
The rpm will hang up after letting off the gas slowly. Putting a helper spring to return the throttle wont help i did that and it just puts extra
pressure on carby no 1 and dosn't transfer this no carb 2,3 and 4.
I think you are on the money with the tiny springs in between each carby if they were very very stiff there would be less twisting slack between each
carb.
The power of the r1 carbs is great but drivability is a real pain becuase of this. When i spoke to a good friend who is a real bike guy he said .
well they work nice on the r1 bike so it's somthing you have done wrong when fitting them to the car.
All i can think of is my manafolf pipes are not the perfect offset to the carbs and the very very small differance is taken up by the soft rubber
tubing. but that said it could be putting some twist on the carb bank? but i don't think so .
I still think its a pore design and will be trying some cbr600 carbs that have the throttle linkage in the middle next week.
I would like to hear how other people get on with the r1 carbs because other than the sticking they are a great carby.
kurt
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bricheun
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| posted on 17/2/07 at 02:03 PM |
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I have partially fixed it by swapping the "screw spring" with the "return spring". If you notice the balancing spring is much
stiffer than the return little spring. It fits nicely.
I have also ever so slightly "unbalanced " the butterflies so that on return, the 4,3,2 butterflies closes just as 1 closes. But this does
mean that number 1 is always slightly ahead of number 4 3, and 2.
I used a small diamter tube to listen for the balancing when I pull the throttle ever so slightly and return to idle, listening for similar hissing
sound when fully installed. Not when the carbs are out of the car..as you said, the manifold and constant movements do make the carbs slightly out of
tune.
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jacko
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| posted on 17/2/07 at 07:02 PM |
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Hi Bricheun i think the zx9r carbs are the same fitting as yours i had a idea about this problem with the pipes try fitting rubber o rings in the
groove no the carbs then put supper glue on it push the pipes on and let them set before fitting the clip + trim a small bit of pipe away were the
springs are
Jacko
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kurt t
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| posted on 18/2/07 at 06:31 AM |
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Well I fitted a set of cbr 900 carbs today they are only a 35mm rather than 41 of the R1 carbs
the return linkage on each carb is so much better than the yamaha setup. nice strong spring on each carb throttle pulling from the middle of the 4
carbs .
So there is no throttle sticking and a very fast return to idle .The only problem i om having with them is that with the r1 carbs i used a r1 electric
fuel pump but the presure is to high for the cbr900 carbs that a graverty fed carb.
but running on whats in the fuel bowls nice crisp throttle seem like a good match to the engine.
r1 carbys now for sale.
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Browser
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| posted on 19/2/07 at 08:35 AM |
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Are any of you using the original mounting rubbers on inlet and outlet? As someone else has said, if there's a slight mis-alignment in the
manifold or adaptor stubs this may be enough to cause your problem.
Have they always done it? If so where did you get 'em? Do they do it if they're not fitted to the car? Could possibly be a bent spindle. I
remember Dave Walker in CCC mag one saying about mis-aligned throttle butterflies. His method for correcting this was to slacken the butterfly
mounting screws slightly, snap the throttle open and shut a few times then carefully re-tighten them.
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bricheun
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| posted on 20/2/07 at 06:04 AM |
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It could well be misalignment of the spindles, but it seems to have sorted itself out now.,.wierd. But it drops to idle now. Though not immediately to
idle (900-1000rpm), it drops to 1200 real fast then as you idle it drops down within 10-15 seconds.
I have cut the rubber boots to make sure it does not snag the springs. I am hesitant to fit the CBR600 F3 carbs because they are smaller..I think
it's 35mm compared to the 37 of the ZX6R. Plus I have to do all the mounting again and thats not fun...
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