NOT MUCH,, it is supposed to store the extra air fuel mixture that comes back thru the intake instead of going thru your carburetor a 2nd time.. IT DOES NOT IN ANYWAY GIVE YOU HORSEPOWER OR TORQUE,,!!
it may help with smother throttle response at low rpm.. i might take mine off if i dont see any kind of gain.. i will see after i re-jet my carb due to RM 85 pipe install and UFO style K&N air filter..
right now after all my hard work and making sure its exactly 66cc including hose and fitting volumes,, it just seems to make my idle very hard to adjust and dialed in..
i look at it this way some bikes it might work great on,, and others not so much.. like all other things with these bikes its a flip a coin crap shoot !!
they must do something cause they have been used on stock factory motorcycles, ATV's, Dirt Bikes and other toys and there is a market for them,, Like I said its a case by case basis,, some people RAVE and some RANT,,, MY OPINION,,"" NOT WORTH ALL THE HYPE,, but nice piece of eye candy when you make it look like a NOS bottle..