Removed my gas tank, found item disconnected. 07 FJR

[bajaleo]

While trying to figure out why I lost my headlights, I removed the gas tank. I found a device laying on top of the cylinder head that looks to have been disconnected by the PO. It appears to be a vacuum valve of some type with an electrical connection.

I think I should look like this. From youtube video I found,

Any ideas why this would have been disconnected?

Thanks, Leo

 

[bajaleo]

Ok, it's called "air cut valve assy". Mine's not connected. Appears to have been bypassed at some time in the past before the bike was mine. What does it do?

 

[jmgrif]

Not sure but may be part of the Pair system which I think recirculates unspent vapours to be re-introduced? It can be totally removed and block off plates can be installed for a less cluttered appearance!

 

[ionbeam]

The Air Injection Solenoid (AIS) injects air into the exhaust stream just after the exhaust valves; there is a small air passage that ends right where the exhaust head pipes attach to the valve head assembly. When the engine is cold (coolant thermostat is closed) and decelerating, and when a warm engine is at idle the ECU (computer) turns ON the AIS by turning OFF 12 volts (your disconnected connector). This injects air into the exhaust allowing a secondary burn of excess fuel in the exhaust head pipes. This is done only as an emissions control device and has zero performance influence. When the engine is cold and the AIS injects air on deceleration it does cause audible popping which is harmless.

The air injection is timed by reed valves which only allows air injection when the exhaust valve opens and creates negative pressure. Over time the reed valves will start to crud up and may hang a bit, but it doesn't really affect performance. A very popular modification is to install Wyn-Pro blank off plates. These are made by Dave here on the Forum and are very pretty pieces of engine jewelry. They let you lose the AIS valve and all the associated plumbing which appearance wise really cleans up the top of the engine.

The issue you have is when the connector is unplugged from the AIS it leaves the valve OPEN (ON) all the time. The AIS valve only closes when 12 volts is present. If all the pipes are properly blanked off you should be OK. If the hoses are not blanked off you should either reconnect the AIS and associated plumbing or drop Dave a note and score some blank off plates and be done with the whole mess. The way Yamaha designed the AIS system to be OFF only when there is 12 volts almost looks like they made it so you couldn't defeat the AIS by unplugging it

 

[bluesdog]

The air cut-off valve is part of the PAIR air-induction system. Some, myself included, bypass this as part of blocking off the entire PAIR.

From the FSM:

The air induction system burns unburned exhaust gases by injecting fresh air (secondary air) into the exhaust port, reducing the emission of hydrocarbons. When there is negative pressure at the exhaust port, the reed valve opens, allowing secondary air to flow into the exhaust port. The required temperature for burning the unburned exhaust gases is approximately 600 to 700 °C (1112 to 1292 °F).
The air cut-off valve is controlled by the signals from the ECU in accordance with the combustion conditions. Ordinarily, the air cut-off valve opens to allow the air to flow during idle and closes to cut-off the flow when the vehicle is being driven. However, if the coolant temperature is below the specified value, the air cut-off valve remains open and allows the air to flow into the exhaust pipe until the temperature becomes higher than the specified value.

You could purchase a set of block off plates, (wynpro), or use plugs to bypass the PAIR