gas caps

[michael]

Are all airhead gas caps vented? Can a gas cap from a 1992 R100RT be used on a 1978R100/7? Thanks

[Kurt in S.A.]

RealOEM suggests that the part number covers a wide range of bikes:

http://www.realoem.com/bmw/enUS/part?id ... 1252307125

Kurt in S.A.

[Wobbly]

All Airhead fuel caps are provided with vents, but not all these vents are in working order. As an example... Later models had little rubber flapper valves internal to the cap that were supposed to stop liquid spills (and thereby fires and pollution) in the aftermath of a lay down event. Those flaps are famous for getting stuck in the closed position. So if you buy a used cap it's always best to blow it out with high pressure air to break those flaps loose.

The Oilheads I've worked on (not saying ALL Oilheads) had un-vented fuel caps. Tank venting is done by hoses internal to the tank, so that fumes could be gathered and recycled into the fuel injection system. These hoses and pipes come out when the fuel pump assembly is removed from the fuel tank, along with the fuel pickup filter, the fuel level sender, and a host of other plumbing.

[Seth]

yes (regarding Oilheads).
I have an '02 R1150RS in Denver.
The PO did a bmw airhead charcoal canisterectomy, but just sealed the line that went to the canister.
When riding, the tank would create a huge vacuum (not good for the pump).