Venting the fuel cap

78jotadave

78jotadave

Hero member
Location
Palm Desert, California. (near Palm Springs)
So I bought and installed a new 75mm rubber gasket under the fuel cap as the original had deteriorated into 3 pieces. So now it seals the tank up to the point where after 30km fuel stops flowing to the carbs, popping open the petrol camp there's a whoosh sound and fuel flows once again. So what is the remedy for this problem? Does anyone have a solution?
 
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Not sure if this will help you, but I had a similar problem w/ my 750 cap. The original "gasket" was a circular piece of leather and I replaced it w/ Fel Pro gasket material. I could hear slight hissing w/ a similar "popping" when releasing the cap. I took the inner cap housing apart and noticed a small vent hole and punched an aligned hole in the gasket, and no more hissing. Your cap may be different, but look for a vent hole inside the cap that releases built up pressure from the gas fumes in the tank.
 
78jotadave said:
So I bought and installed a new 75mm rubber gasket under the fuel cap as the original had deteriorated into 3 pieces. So now it seals the tank up to the point where after 30km fuel stops flowing to the carbs, popping open the petrol camp there's a whoosh sound and fuel flows once again. So what is the remedy for this problem? Does anyone have a solution?
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Had that happen to me too. Teddy is in the money. I found the vent hole blocked, but frankly I struggled to understand how it actually worked. But gave up scratching my head once it worked properly.

On the other spectrum, like Vince, had another one that, when too near full, leaked fuel out under brakes.
 
Again, I have a 750 that may have a different cap than yours, but the gasket housing is spring loaded and locked in place w/ notches. I depressed that and rotated it to free it from the outer cap. A small vent hole is visible and was obstructed by the gasket. I punched a hole in the gasket to line up w/ the vent hole. It now seals w/o creating hissing pressure.
 
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