What do these do on the carb?

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RickTaff
Posts: 21
Joined: Tue Jul 28, 2020 1:49 am
My Bike: zxr 750 1991 J1

What do these do on the carb?

Post by RickTaff »

See in the attached photo, theres obviously 4 butterfly valves which open when throttle is opened. But in between each pair of openings is a screw with a spring.... theres 3 altogether. 1 between first 2 butterflies, 1 between next 2 etc. Are they idle adjusters?

Reason i ask is one of those screws on my bike is missing its spring, and either that is the reason for its erratic idle,.... or the butterfly is slightly sticking. Because the minute you adjust those springs, the idle drops, and will also fly up if you adjust them the wrong way too much :smt003 :smt003 :smt003

So im curious is it the missing spring causing an issue, or perhaps a sticky butterfly valve.

Everything else on the bike is sorted now. All jets, floats, needles, etc etc cleaned and all fuel lines cleared and cleaned.
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banner001
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My Bike: ZXR400 L4
Location: Nuneaton

Re: What do these do on the carb?

Post by banner001 »

They are the carb vacuum adjusters, they allow you to ballance the carbs and are 100% essential to the correct running of the carb
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
RickTaff
Posts: 21
Joined: Tue Jul 28, 2020 1:49 am
My Bike: zxr 750 1991 J1

Re: What do these do on the carb?

Post by RickTaff »

banner001 wrote:
Fri Feb 05, 2021 11:13 pm
They are the carb vacuum adjusters, they allow you to ballance the carbs and are 100% essential to the correct running of the carb
excellent, cheers. Good job i am borrowing a mates carb balancer soon. Failing that, itll be heading into a garage to be balanced.
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