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Author: Subject: bike carbs revs slow to drop
legend

posted on 19/9/16 at 08:41 PM Reply With Quote
bike carbs revs slow to drop

still building car. 1.8 zetec on zzr1100 carbs using esc unit with vacuum advance when i rev the rpm is very slow to come down have 4 vacuum pipes to small chamber to esc if i remove vacuum from esc the revs come down quick .Is this due to the esc keeping the timing to advanced or is it normal with a esc unit ?or carb fault the throttle is closing on all carbs ok and no air leaks .or do i go to nodiz ?
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kingster996

posted on 19/9/16 at 08:51 PM Reply With Quote
The vacuum pipes need to be blocked off. They are for balancing and also to open a vacuum tap on a bike fuel tank.

This can be caused by a few things but the two common ones are butterflies out of balance or throttle return is not up to the job. Bike carbs usually have two cables with one that snaps them shut when you roll the throttle off. On a car you have one so rely on the return Spring. Not usually a problem but can be. Most likely will need balancing.






I used to be indecisive, but now I'm not so sure

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legend

posted on 19/9/16 at 09:02 PM Reply With Quote
vacuum pipes come from manifold not carbs .and have checked balance all ok
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CosKev3

posted on 20/9/16 at 07:37 AM Reply With Quote
Using standard return spring on carbs?

Usually need a stronger spring as above,due to the bike having a twin cable set up

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minitici

posted on 20/9/16 at 12:53 PM Reply With Quote
Fit the opposing cable and run that to a big spring to close the throttle.
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chris

posted on 20/9/16 at 02:21 PM Reply With Quote
I found fitting a good spring to the pedal works well then the spring on the carbs is only returning the cable and not the pedal aswell
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Slater

posted on 20/9/16 at 02:59 PM Reply With Quote
I had the same issue, and fitted a throttle return spring as per pic below. Just a short bit of cable fitted to the quadrant and some springs and "home made washers" it actually works very well. Since the pic I've added an extra slightly stronger spring.

[img] Throttle Return Spring
Throttle Return Spring
[/img]





Why do they call Port Harcourt "The Garden City"?...... Becauase they can't spell Stramash.

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legend

posted on 20/9/16 at 07:49 PM Reply With Quote
yes i did think this would fix it but even operating the carb throttle by hand and then holding closed made no difference mmm
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legend

posted on 22/9/16 at 07:20 PM Reply With Quote
mmm found air leak on manifold my poo welding rewelded today refit soon
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