Flip your gas cap. See the hole with the tiny rubber gasket? See the cone or the taper that pivots into that hole you close the cap? That is your vent you want to keep open.
Sit on the bike, as if to look down. See the left fitting out? That is a washing or weather drain, you fill the tank cap area with water.
See the other fitting out the tank, we have the vent and drain fittings figured out? See the other one remaining? Keep that hosed down and away from the mufflers. This is when you over fill the tank, this slosh vent tube captures the gas, sends it down to the return pump, down the canister.
And when you send in a thread saying your bike runs like shit, you just topped it off, well, if we are all in the fuel follow, this dumps fuel into one cylinder each time, while the other cylinder is used for the air sucking pump on that stroke all the time. You burp out the excess fuel into the other cylinder until it cleans out or evaporates on it's own you let it sit, eventually.
If you blow into that cone, you can make that hiss noise everyone hears now and then is the tank cap rubber stretching like a balloon end letting the air out, kind of, "funny noise is."
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