The air flow of this pipe is controlled by a solenoid which in turn is controlled by the bikes ECU/ CDI.Ī bike with a leaner fuel mixture of course uses less fuel in proportion to oxygen and in theory the additional oxygen content is said also to help burn off any unburnt fuel in the exhaust. From an emissions perspective the introduction of fresh air into the flow can certainly make the exhaust gases appear more dilute when measured. This comes at a cost though, a lean mixture can cause the piston to run hot. the piston can subsequently over-expand and can seize inside the cylinder in which it is suddenly too big to move up and down within. This is an especially high risk with tuned engines that run lean.
