Originally Posted by JRWooden
I can't find any specifications on the valve in either the BMW manual or the Haynes manual, but was told by my dealer when my tank was replaced that the valve did not open until something like +2.0psi on the pressure side, and several inches of water on the vacuum side. In other words the valve, by design allows some "modest" pressure or vacuum to build up in tank... (this is on a 2009 model). I also can't find any specs on the (rumored) newer design that uses a sintered core ...
If anybody else has specifications please post!
Since this valve is a separate item from the "tip-over" valve, I'd really like to know if this valve has any function other than to reduce emissions (by reducing the amount of "breathing" that the tank does which would let more fuel vapors into the atmosphere when the bike is not running).
That is not the case with my valve. As I noted in a post somewhere....might be on f800riders forum.... But if memory serves me correct ...... Mine flowed free with no restrictions....INWARD to the tank....and opened up about 4-5 psi AWAY from the tank. One note.... if vacuum was applied to the away side...( against the arrow) it would flow free with no restrictions. It only too a minute suction...and it would flow free against the valve. There should be no vacuum......not even a little...... but I can see a less than 5 psi pressure build up.