Re: Gas/fuel tank breather
I also found that a check valve solved this problem. In the end I went to an off-road bike/ATV store and bought a check valve for about $10.
My breather pipe is located at the front of the tank, and I mounted the check valve at the same height as the filler cap, attached to the vent pipe by a length of rubber hose.
Since adding this in, I haven't had any fuel spillages and petrol odour is less (using downdraught Dellortos mean you always smell it a bit).