Whats up with these gas tank caps?

What I did was to drill a very small hole with my pin vise drill on the top side of the cap (cant see it). Then I drilled another in the middle underside of the cap.

I think what happens is that the gas sloshes and also gets warmer and then when it splashes up on the cap gasket, the pressure tends to force it out. When I vented my tanks, I never had a problem again.

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If it ain't broke, and you mess with it long enough, it will be.

I drilled a hole in the top center of both my caps. What was happening on my bike was the fuel would slosh and the engine would warm it and it would pressurize the tank a little, then when the fuel splashed up near the filler neck, it was forced out around the crappy gasket.

I haven't had any problems since I drilled them.

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If it ain't broke, and you mess with it long enough, it will be.

Great idea, I think I'll make one and put it on today. I don't have a problem because my tank is at a funky angle. But one never knows what will happen on any given day.

Gas is really known to expand in the tank. They used to say fill your car first thing in the morning and you get more gas because it is more dense. It will expand as the day goes on. So I wouldn't fill mine when its cool then store it. Fill it then ride it I think would be best.

That is true about the expansion I have filled my car then driven home a few blocks left it all day and found a puddle at noon.

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Just to be sure is this the same cap you guys are talking about.Notice vent hole inside rim(very bottom of pic).It seems to allow gas to pass through and around any seal you might have with "boss".Ron
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I gotta say - my cap is different. No vent hole like that. Still leaks.

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No vent holes in mine.

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If it ain't broke, and you mess with it long enough, it will be.

Maybe I'm lucky, but my cap and tank have been great. I fill mine up, no sloshing. Today I had to take the tank off to install a new exhaust pipe, and I even dropped it when it was full of gas, it didn't hit the floor because the fuel like was still connected so when I dropped it, it dangled from the carburetor. I freaked out, when I realized I dropped it and it yanked by the fuel line, I totally expected gas to leak out all over me, the bike, and the soft wooden floors of my shed, but not a single drop came out! It was amazing. It seems to vent fine too, but the weather has been cold since I've gotten it. Also, I always use a funnel when I put gas in the tank, to make sure I don't get a drop on the tank when I fill it up.

For three years not one drop has leaked from my cap. I fill it all the way to the top, no problems.

I think I will see if I can get a new cap.......

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