Never had this happen before. Went out riding yesterday, started with an almost full tank. With about a quarter tank remaining, I stopped at a gas station to fill up. After unlocking the gas cap, I couldn't lift it. After pulling considerably harder, it finally opened with an obvious "whoosh" sound, it was vacuum locked. I guess I thought the tank was vented enough that this wouldn't happen. Anyone else had this happen?
Yep. Filled up and after 80 or so miles later the bike is running really rough like it is not getting enough fuel. As I inserted the key to open the tank, I somehow pushed the gas cap down to the point where I heard the "whoosh" sound. I recalled that I hadn't securely closed the cap at my last fill up.
Basically, what I found was that you have to firmly close the cap after each opening in order to make the vent clear for operation. Otherwise the vent will not function properly.
Easiest way to ensure the cap is correctly fitted is to push the cap down (not the key) until the key lock spring returns to normal (key can be removed). I've always done it that way and have had no problems (yet).
It's the life of the unemployed. I watch comedy on netflix and combine it with my natural ability to be a smart ass. Sprinkle a little disillusionment and anger on top and PRESTO ... a good reason to dislike me. LOL