24mm Kiehin CV Air Cut Valve

[Rocketdog]

Here's my poor explanation of how a Air Cut Valve works. Let me know if I left anything out.

I’m going to attempt to explain the operation and purpose of this circuit in the Keihin CV carburetor. The Air Cut Valve is an air bleed to the pilot jet that can richen the pilots mixture under high vacuum conditions. These conditions would normally occur during sudden deceleration and abrupt throttle transitions. There may be others. But normally it’s just for lean deceleration backfire or exhaust popping.



In normal situations the valve in the carb body is in the open position. The large diaphragm spring presses the actuator pin against the plastic valve and keeps it from seating. This allows air to pass around the actuator pin, since the pin is much smaller than the brass valve seat, under the pins diaphragm and into the pilot jets circuit.





When a high enough vacuum signal reaches the hose barb, on the outside of the diaphragm, it overcomes the diaphragms spring pressure and allows the valve in the carb body to close on its seat. Thus stopping air from bleeding to the pilot jet circuit and richening its mixture.

Here are my very poor sketches of the ACV circuit. I can’t find a decent cut away of one anywhere.

Normal



High Vacuum



I hope this helps.

RD

[jmkjr72]

thanks for the post this gives me something else to look at if the cdi doesnt resolve teh issue with the scoot im working on