Hi
I have a zx9r b model engine and on top of the valve cover there 2 holes with down into the engine.
onto these holes there is some kind of thing and from there tubes to the airbox.

but why have they made these vent holes and what do they do??
and more indportently er they nessesary?

hope some one can help.

best regards Esben

We allready had a long discussion about these Vents. Technically they are not needed, they are just used to
return a little portion of the exhaust stream back into the combustion cycle to keep co emissio lower.

Boa,das krieg ich in englisch nicht hin.

Das ist die Abgasrückführung,Secondary Air into the airbox.
Die kannst du stillegen,bringt etwas leistung,weil dann keine heissen abgase mehr in die Airbox kommen. einfach die beiden löcher im ventildeckel verschliessen,und das loch in der airbox schliessen.

Yes Sturzflug is right there, you can remove the controlling vent on the top of the cover and adjoin the two tubes
with a pice of pipe. Since no warm gases will be returned to the combustion cylce, you will get a slightly better
perfomance due to an increased filling of the cylinders with air/gas mix from the carburetor.

thank you for your answers..

as far as I can feel there is sucktion i these holes?? can that be right??

The holes on the ventcover should have some pressure on them coming from the exhaust port, but no sucktion