What does the AIS do to affect performance?

I'd like to know what the smog thing actually does to hurt the motor. I still have the system on mine and I've noticed that when I get off the throttle after winding it out, when I get back on the gas it takes it a minute to pick back up. I wouldn't call it a hesitation. The motor try's to rev up but no power. Its like there is something restricting it. Does the AIS system have anything to do with that and if not, what does it affect?

I got the ais removal kit from yamaha. took about 2 weeks to get. I have read somewhere it didnt hurt power. Its just makes your bike pop,pop,pop when you let off the throttle. I didnt notice any improved performance, but the ais probably weighs 2 pounds and, it makes it easier to work on the carb when its removed too. All it does is let air into the exaust so you get cleaner exaust. Its what makes the wr green sticker :thumbsup:

I doesn't affect the performance at all. Removing it cleans up the appearance a little and makes servicing a lttle easier but mostly it stops the popping on decel.

Since popping on decel is a telltale sign that you have a lean circuit, normally the pilot, the AIS can mask the problem making it difficult to get the jetting correct. Also, removing it is a nice little slap in the face of all the enviro-nazis at CARB who demanded it because dirt bikes are BAD :thumbsup: :thumbsup: ...SC

I doesn't affect the performance at all. Removing it cleans up the appearance a little and makes servicing a lttle easier but mostly it stops the popping on decel.

Exactly as Dan says. This simple valve uses manifold vacuum to meter the amount of fresh air via the air box to be pulled into the exhaust stream. This help in cleaning up the unburned hydrocarbons. We have assumed that this fresh/cold air is what causes the popping on de-cell. Remove it and all you have really done is lost a pound of weight. I doubt anyone can attribute the AIS to any sort of performance gain or lose.

Call me crazy, I just did this mod, rejetted to specs and it seems the throttle response at low end is slightly better?????????????????

Thanks for the info. I was leaning in that direction but not sure. Mine really doesn't pop like you all are saying. I've took out the snorkle and cut the holes in the side of the airbox. The wire and throttle stop were done when I bought the bike and I took the insert out of the muffler. I've got a 48 pilot and a 170 main and the fuel screw out 1 3/4 turns with the stock needle and it runs great. I'll get a little more in depth with the jetting when I get a pipe. Does anyone know why after I rev it all the way out and let off, why it doesn't pick back up when I get back on the gas? It takes it a second or two for the power to come back on. Mabey the fuel screw is turned too far out? Help please. Once I understand how the FCR works I can take it from there.

I'm in the "doesn't make a difference" boat... Honestly, I can't tell if removing the unit really helped make the bike any better...

Also, removing it is a nice little slap in the face of all the enviro-nazis at CARB who demanded it because dirt bikes are BAD :cry::confused: ...SC

:thumbsup::bonk::confused:

What I've noticed too is that after removing of the AIS you can reach faster the lower RPM which is good for those who prefere engine braking :thumbsup:

I'm one who always used some engine braking. My first few rides, coming into fast corners the lack of engine braking threw me.

After the AIS removal and some jettng it rides and engine brakes much better.

AND, I beat the tree huggers!

AIS is for Green tree Huggers (or where required by law)

The Tuning fork company RECOMMEND removing it for "closed course use" - that means "BIN IT"

As stated above: without AIS; easier to service, looks better, helps relieve decel pop, makes fine tuning the jetting easier < more transparent> , saves weight...any more reasons? More performance is not the primary motivator like lots of other easier mods!!

IMHO I think the Run-on is probably more due to the ACV interference which affects the pilot circuit jetting - another story though.

Enjoy :thumbsup:

Do you guys know if the 49 state wr450 has the ais or is it just the California model?

As far as I understand all 05 and newer WR450's have AIS. I purchased mine in Ohio and it was AIS equipped.

My bike's run-on disappeared after teh AIS removal and rejet. Can't tell which did it cuz I did them both at the same time.

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