25-01-14, 10:49 AM
(23-01-14, 10:31 PM)Gnasher link Wrote: This type of butterfly exhaust valve is not an EXUP (Yamaha) or a SET (Suzuki) which are designed for mid range boost and are mounted in the downpipes or directly afterwards e.g. MK1 Fazer 1000. These single butterfly valves are mounted in the exhaust link pipe just before the end can are a "noise valve" to help them get through ever tougher noise restrictions. They help keep the weight and size of standard silences down often there's a premuffler box hidden under the bike or tucked up somewhere, they're controlled by an actuator hidden in the tail hump linked to throttle position i.e. the valve matches the throttle 1/4, 1/2 etc. They work in a similar fashion to EXUP so are often referred to as such, EXUP valves in the original sense are no longer needed thanks mainly to fuel injection these days the MK11 FZ1 only has a single butterfly.
Interesting. In that case they can probably be junked.