Thread: Leaky gas cap?
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Old 12-09-2011, 07:16 AM
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Allen_Wrench Allen_Wrench is offline
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Default Re: Leaky gas cap?

Originally Posted by GearNut View Post
Leather makes for a decent gas cap gasket material. Inner tube rubber will eventually swell up to almost twice it's original size.

Edit: Sheet cork, available in hobby stores, also works very well.
Inner tube rubber also dissolves in petroleum products. I have personally done this to prove a point. Leather and cork aren't too bad. But when I built my tank out of a softball bat, I realized I would need to make my own vented gas cap.

I used a large, threaded brass fitting for my bung which had a companion threaded collar. I made a brass disk to close the end of the collar and turn it into a cap. I used a large ball bearing and a hammer to dish the disk a bit. I then drilled a hole for a rivet in the center and a vent hole just off-center, in the disk. I made a Nitril rubber washer to fit inside the disk.

Nitril is ideal because it is NOT dissolved by gasoline. First I soldered the disk into place at the open end of the collar. Then I riveted the washer to the inside of my cap with a small brass washer in between. Air comes in through the vent hole and can get past the Nitril washer, but fumes can't blow out through there - the washer seals against the disk. It is designed, however, to vent from inside if you blow VERY,VERY hard. This is a stopgap against pressure buildup.

"There is nothing wrong with wanting a motorbike that is an extension of your personal taste and fashion sense; if you must ride somewhere, I say do it with style!"

Last edited by Allen_Wrench; 12-09-2011 at 07:23 AM.
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