bung hole vent help
Road Master
Joined: Jan 2008
Posts: 1,073
Likes: 6
That little tube is your over flow tube. It's connected to the little tube at the bottom of the tank that connects to the hose that runs down and drains to atmosphere right in front of the rear wheel.
The gas cap is vented one way only - it will hold pressure but it will allow air in.
As the gas / tank expand and contract from heat, that tube allows air (most of it is gas fumes) to be expelled safely.
Plugging that tube is what you might call a bad idea as it will pressurize your tank.
The height of the tube is also significant, though to a lesser degree.
As the gas / tank expand and contract, it's very possible that fuel will get into the filler neck. Rather than having it get all the way up to the top of the tank where it'll pour out of the tank if you pull the cap, it pours down that little tube and onto the ground under the bike.
Cutting it lower will cause your bike to dump gas earlier. It probably won't be an issue, but it's something you need to be aware of.
That little tube, incidentally, is how I transfer fuel from my secondary fuel tank into the bike's tank. Parked in the sun on a hot day, my fuel system gurgles quite a bit as air is expelled from the bike's tank into my secondary.
The gas cap is vented one way only - it will hold pressure but it will allow air in.
As the gas / tank expand and contract from heat, that tube allows air (most of it is gas fumes) to be expelled safely.
Plugging that tube is what you might call a bad idea as it will pressurize your tank.
The height of the tube is also significant, though to a lesser degree.
As the gas / tank expand and contract, it's very possible that fuel will get into the filler neck. Rather than having it get all the way up to the top of the tank where it'll pour out of the tank if you pull the cap, it pours down that little tube and onto the ground under the bike.
Cutting it lower will cause your bike to dump gas earlier. It probably won't be an issue, but it's something you need to be aware of.
That little tube, incidentally, is how I transfer fuel from my secondary fuel tank into the bike's tank. Parked in the sun on a hot day, my fuel system gurgles quite a bit as air is expelled from the bike's tank into my secondary.
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