What are air cut valves?

Did some general maintenance stuff the other day. Noticed two vacuum type hoses meeting between the cylinder valley that didn't apparently go to anything, but had a plastic nipple in each, that looked to either be broken or snipped off of something. I had known about the one going down in front to the lower right fairing, but had just found the other going down under the bike in front of the rear wheel. As best I can figure, they go to the AIR Cut Valves, but I'm not sure what those are for, if they were intentionally disconnected by a PO or were broken over the course of the years and I have no Idea where they were supposed to be connected under the tank / carb area........

Anybody got any Ideas? I didn't really think anything's been wrong, don't know if I've even missed these things not working. Don't know if I should even care that they're not hooked up......

Creole

Can you post a picture of what you found? That could help a lot.

Air cut off valves reduce idle air when engine braking to reduce popping. No hoses connect to them, it's all internal to the carburetor.

Maybe I should go look again. I came up with the Air cut valves by the parts breakdown microfiche. Pictures would be hard to get because of the location of the hose ends without tearing down the bike.

http://www.yamahapartshouse.com/oemparts/a/yam/500441cef8700209bc78e9e1/air-induction-system

Part #'s 46 and 10 are listed as the Air cut valves, and 53 & 19 are what I believe are the two "vacuum" type hoses that terminate somewhere around the carbs. I am not sure what they are supposed to connect to, or what the air cut valves do.

Here is a pic of the hose end that can more easily be seen. This one goes up front to part #40 behind the radiator.

The hose not seen in the picture does indeed go to part #10 from the link in the previous post.

Thanks[

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Ok, not air cut off valve.

I don't have an RSV here to look at but that looks like emissions control - feeds air into the exhaust to help reduce unburned hydrocarbons.

Those valves should have vacuum hoses connected to them.

Thanks,

I assumed it was an emission type thing, based on location and all the tubing routing. The vacuum lines are in my opinion (just based on what I can see) part of the control system. Just can't decide where it gets the vacuum from- carbs, manifold, ect..?

I don't exactly remember, but they are vent lines coming from either the carbs or airboxes. They are supposed to be open and not hooked to anything on the end you showed in the pictures. I too scratched my head for awhile when reassembling after the valve adjustment on what I was missing.

For what it's worth, attached are a few of pictures of the rear AIS unit from a 2003 RSV.

Gary

aaaahhhhhh, Yep that looks like the thingabob right there. And Squidly, It did look like someone snipped the nipple off, because it's still in the end of the hoses with the clamps around them, but it makes me wonder if they plugged the manifold nipples these hoses belong on, when they removed them.

At any rate, if these were removed intentionally, and it doesn't hurt anything if they're off, then I'll quit worrying about it.

Really appreciate the help folks

That looks like part of the AIS system that the G2's have. There are 2 units, 1 is behind the radiator and is plugged into #3 intake manifold nipple. The 2nd one is down behind the underside of the engine, by the coils and is hooked into the #2 intake manifold nipple. That hose in your pic more than likely hooks up into the #3 manifold. Many folks discoinnect the AIS after the warranty is up if they start to get popping. Some here are against that, some folks do it. I'll bet thats what your looking at....

Squidley

So glad I came across your post today. I recently pulled my carbs and carb boots for maintenance and I was sure that the vacuum line from the rear ran to the number three boot nipple. However the manual is showing it running to the number 4 boot nipple. I am attaching the diagram from the manual which shows line F running to carb joint 4. Since you agree and everything else I have seen (such as pictures I have found showing it attached to the number three) I am assuming that the manual is wrong or I am reading the diagram wrong.

AIS.pdf

The A.I.R. system sends air (oxygen) to the exhaust. This causes any left over fuel in the exhaust to burn. During periods of deceleration extra fuel is wasted into the exhaust. This could cause popping and detonation during deceleration. To prevent this a vacuum controlled valve (vacuum is very high on deceleration) cuts off the flow of air into the exhaust during deceleration.

Mike