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Old 09-06-2012, 10:03 PM
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GearNut GearNut is offline
Motorized Bicycle Elite Member
Join Date: Aug 2009
Location: San Diego, Kaliforgnia
Posts: 5,106
Default Re: vented gas cap leks fuel?

All I can suggest is using your idea to run a tube off of the cap itself or installing an auxiliary vent in the fuel tank. An internal tube running from the top of the tank near the filler hole and out the bottom floor of the tank. Like a stand pipe would be installed.
This is how modern *sold in California, street legal* motorcycle tanks are vented. It is the only way the Mfg's can vent the tank through a vapor canister to comply with the CARB reg's. The "vented" caps sold in California only vent air in, nothing out, so as to not cause a vacuum in the tank as the fuel level drops.

Yeah, it sounds like alot of extra work, but if you wanna keep the look of the cap clean without a hose on it...

I have a suspicion that you are developing pressure inside the tank as the gas sloshes and vibrates inside, causing it to vaporize some. The pressure has nowhere else to go but through the gas soaked screen in the cap forcing the gas out of the screen and out the vent hole. The stand pipe vent would solve this problem.
"It's a chinagirl. It's a sometimes fun little engine that often will break your heart. It's disposable.

Does not come with a fortune cookie."

Last edited by GearNut; 09-06-2012 at 10:10 PM.
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