air cut off switch

i have an 82 kz1100A shaft, and i was looking at it last night and saw the assembly for the air cutoff switch. didn't even know what it was till i looked into it. how exactly does this work? it's a far cry from anything on my previous bikes. i deduce that it somehow acts like a choke.

I believe what you're seeing is part of Kawasaki's Clean Air Suction System(CASS) a type of smog reduction system that introduces fresh filtered air to help combustion.

There are reed valves under the covers that have two rubber hoses connected to this air valve. Most riders have removed this sytem and blocked off the valves with machined plates available from several sources.

Myself,I'm going to remove my bikes CASS when the weather gets warmer. I ordered the kit from www.tpoparts.com # TPOHRSMOG. It comes with two block off plates,screws,vinyl caps and instructions.

It doesn't act like a choke. It injects air into the exhaust. This doesn't really affect combustion or running since it only affects burning outside of the combustion chamber. It is set up to not inject air when you close the throttle. That's why it needs to sense intake manifold vacuum.

Usually the first symptom of it going bad is big back fires when you close the throttle.

loudhvx wrote:

It injects air into the exhaust. This doesn't really affect combustion or running since it only affects burning outside of the combustion chamber.

Though it does reduce cylinder filling by decreasing the scavenging of the cylinder. When the CASS is operating, low pressure in the exhaust pulls fresh air in through the reed valves rather than spent gasses from the cylinder. Not desirable in a high performance application.

the air cut off he is describing is part of the carb what it does is just that it cuts off air and adds a small amount of fuel on deceleration so the engine wont lean out and afterfire out the exhaust. most of the newer carburated bikes and atv's come with this because they are jetted so lean down low.

I don't recall KZ1100 having that type of setup Tim. Generally that's found on big single cylinder engines.

There's a crank case scavanging affect that is a plus for for the clean air system. Everybody bails out on it and forgets about that benfit.

Interesting, how does the clean air system scavenge the crankcase? On the 550's, there is no connection from crankcase to the clean air system except that they share the airbox. I doubt the clean air contributes much vacuum to the airbox relative the engine intake.

Just to help you guys discuss this is a diagram of how it works on my 650. It allows air in while deaccellerating to burn unburnt fuel. (click to enlarge)

bluemeanie that is exactly what i'm looking at on my 1100. never seen anything like it. i appreciate everyones response. my bike does backfire when i let off the throttle, i assumed it was running to rich. this may offer another explanation.

mastermudd wrote:

bluemeanie that is exactly what i'm looking at on my 1100. never seen anything like it. i appreciate everyones response. my bike does backfire when i let off the throttle, i assumed it was running to rich. this may offer another explanation.

Sometimes, slight enrichment of the pilot circuit will reduce exhaust popping while decelerating with throttle closed.

Whereas, a leaner pilot circuit may increase the popping.

Good Fortune!

mastermudd wrote:

bluemeanie that is exactly what i'm looking at on my 1100. never seen anything like it. i appreciate everyones response. my bike does backfire when i let off the throttle, i assumed it was running to rich. this may offer another explanation.

When that happens you can generally trace it to one of the vacuum hoses that connect the air valve to the intake boots.

Rarely do those valves every go bad. At least they didn't used to :laugh:

It's possible to fabricate a connection to the crankcase breather with the airbox removed to help scavange it.

What's it buy you?

That depends on the motor. On a stocker, not much. On a motor that's been significantly increased in cc, it would be more beneficial.