Author Topic: Air Cut off valve  (Read 381 times)

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Offline Pbfoot

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Air Cut off valve
« on: May 28, 2019, 06:39:56 pm »
So I bought a set of ZG1200 Voyager carbs for parts and I noticed that although similar to the ZG1000 carbs there are no air cut off valves . I'm curious as to the purpose of the air cut off valves and why the ZG1000 carburetors have them but the ZG1200 does not.
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Offline MAN OF BLUES

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Re: Air Cut off valve
« Reply #1 on: May 29, 2019, 07:34:07 pm »
it was part of the Cali attempts at early "P/C"...
None of the 34mm and 36mm "big" Ninja carbs had them either...

just the Vulcans, KLR650, and 250 Ninja's used them.

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Offline RWulf

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Re: Air Cut off valve
« Reply #2 on: May 29, 2019, 08:28:51 pm »
So "Man of Blues" what exactly did they do ? And how did they do what they did ?

Offline NWMike

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Re: Air Cut off valve
« Reply #3 on: May 30, 2019, 02:55:21 am »
At the risk of oversimplification...

It's counter intuitive, but the air cut valve is designed to make up for the somewhat lean jetting and 'after burning' (popping exhaust) one might experience during throttle closed, deceleration conditions.
It cuts off the normal air through portions of the carb passages and idle circuit and actually richens the air/fuel mix under those conditions so combustion occurs in the chamber instead of a misfire and the un-burnt fumes igniting in the exhaust pipes instead.

At least that's my understanding....
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Mike. 
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Offline MAN OF BLUES

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Re: Air Cut off valve
« Reply #4 on: May 31, 2019, 05:58:30 pm »
yep.

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Offline connieklr

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Re: Air Cut off valve
« Reply #5 on: May 31, 2019, 06:25:11 pm »
NWMike got it.

My ’95 with the Delkevics have a nice throaty snap, rumble, and occasional pop when down shifting and coasting to a stop with the throttle closed. Not really objectionable; I kinda like it. I’m sure my removing all the “air injection” stuff is contributing to it.

My DG pipe with a silencer core on the KLR has very little pop to it. The air C/O valve on that bike is fully functional. Kawasaki is right proud of that little KLR diaphragm ($50 before shipping).  Found it on eBay for $15, including shipping. Mine occasionally weeps a little fuel in cold weather so got a spare to replace it if the warmer weather doesn’t swell it up enough to seal it off.
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