Sij
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| posted on 14/4/10 at 12:50 PM |
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xflow with bike carbs over revving on idle
As above when started from cold it idles fine at 900-1000rpm but as it warms up it idles at 2000rpm. Then when I blip the throttle it increases to
3000 rpm. When driving its ok but when I let go of the throttle it idle between 2-3000rpm. I have undone the idle screw to the maximum and sprayed
carbs cleaner down the trumpets. No joy, Any help would be appreciated.
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David Jenkins
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| posted on 14/4/10 at 12:58 PM |
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Im wondering if your butterflies aren't returning to the 'off' position as it warms up. Do you have a return spring on the throttle
cable, at the carb end?
Alternatively, are you sure everythingis fully off when you close the choke?
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GaryM
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| posted on 14/4/10 at 01:12 PM |
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Have you checked that all the throttles (butterflies) are closing completely when you take your foot of the gas?
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Sij
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| posted on 14/4/10 at 01:28 PM |
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quote:
Originally posted by David Jenkins
Im wondering if your butterflies aren't returning to the 'off' position as it warms up. Do you have a return spring on the throttle
cable, at the carb end?
Alternatively, are you sure everythingis fully off when you close the choke?
Yes there is a spring and it does close all the way.
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bbwales
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| posted on 14/4/10 at 01:53 PM |
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Hi,
I had the same with my R1 carbs, only cured it by adjusting the cable so that there was some slack in it, this then allowed the carbs to close
fully.
HTH
Bob
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Danozeman
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| posted on 14/4/10 at 02:51 PM |
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Are they balanced properly?? How much is the pilot screw unscrewed?
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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Sij
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| posted on 14/4/10 at 02:56 PM |
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quote:
Originally posted by bbwales
Hi,
I had the same with my R1 carbs, only cured it by adjusting the cable so that there was some slack in it, this then allowed the carbs to close
fully.
HTH
Bob
I dont think its the cable because when I try to close it with my hand it does not make a difference.
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Sij
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| posted on 14/4/10 at 02:59 PM |
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quote:
Originally posted by Danozeman
Are they balanced properly?? How much is the pilot screw unscrewed?
Not sure if they have been balance but the guy I got them from did say that they were balanced.
The Screw is undone all the way.
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David Jenkins
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| posted on 15/4/10 at 06:44 PM |
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Coming back to this a bit late... when the engine's warmed up, and it's idling too fast, have you tried pushing the quadrant that operates
the butterflies? By "quadrant", I mean the disc or whatever that the cable pulls on.
If so, when you push it closed, do the revs drop? If so, then you have a problem with the throttle closing (sticky throttle cable, not enough return
spring, etc). If not - then I have no idea!
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Fizzer
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| posted on 17/4/10 at 12:20 AM |
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Agree with Dan, get flow meter and balance them, take your time and recheck.
Also check linkages between carbs for looseness or any potential source of variation.
It only take a mild imbalance to cause a very variable idle, sloppy linkages need sorting.
Also, perhaps running rich at idle?
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cliftyhanger
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| posted on 17/4/10 at 06:24 AM |
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Air leaks? has the problem just started?
Try spraying carb cleaner or WD40 etc around all the joints, carb/manifold, manifold/head etc, see is you get a change of engine note. How about
throttle spindles? Older cars had issues with these, not sure about bike carbs...
BUT I would def start by disconnecting accelerator cable, and loosening all linkages first, check balance like that, all hoses, any blanking
plugs/vacuum hoses etc that may be fitted.
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Sij
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| posted on 17/4/10 at 12:31 PM |
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Sorted
The butterfly thing the cable pulls on wasn't fully returning back, So i fitted a spring to pull it back sorted.
Thank you very much for the help guys
[Edited on 17/4/10 by Sij]
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David Jenkins
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| posted on 17/4/10 at 02:22 PM |
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Good result!
(always worth checking the easy things first...)
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