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Blocked breather?
no breather tube...so there one in the cap... if this is blocked excess pressure will look for the path of least resistance.....
 

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did you get a chance to clear that breather hole in the cap...?
Also I havent seen regular fuel strip paint like that.......was the paint like that when you acquired the bike or did it just happen recently...?
 

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Discussion Starter #4
Inside the cap there was a little bit of rust, so I let it soak in vinegar for the night. Then rinsed it with water and baking soda.
Now I'll wait to see if the pressure builds up inside. And I'll take her for a short ride.
I also fitted a new gasket now, a little bit thicker. The cap closes very tight
The tank was repainted about 3 years ago. It is always wet around the cap.
 

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Even with a good gasket/cap seal I remember that once I dropped the bike it still leaked lots of fuel...so its not a "tight seal"
did you get a chance to blow out the cap with compressed air...or clean any holes with a wire?...if you have already got some improvement then maybe its the cap internals...and you just need to clean the breathers well
 

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Discussion Starter #7
I cleaned it with a wire. Should the wire come out the other way? Because it does not. At least not with the cap off the tank
I'm guessing that only when the cap is on the tank and the internal spring is streched then the breathers are fully open.
I will try with compressed air too, and ride with full tank and see what happens
 

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Years ago I had a customer that was experiencing fuel starvation. To make a long story short, it was a plugged vent system in the cap. So, I took the cap apart to properly see why I couldn't get it cleared. It took me a while to find this cap so I could show you, but here it is.

Gas cap all assembled.


With the lip of the cap cover pried open to remove it, there are 2 pieces pressed together and then pressed into the base.
The center piece has another vent hole in it.


With that piece pried out, I found another vent hole in that piece too. You can also see where the water had settled and rust was built up in there.
Sorry I can't find the picture of how thick the rust debris was. But there was a lot of it in there after this 3rd hole got plugged from it.




So there you have it. The reason it's so hard to clear a vent system is because there's 3 small holes in total that can not be accessed without ruining the cap and it's sealing properties. I suppose you could soak a cap in a rust removing liquid like Evapo-Rust, but if it didn't dissolve all of it and left rust flakes behind, it wouldn't take long before one of the holes was blocked again. Maybe Evapo-Rust and a sonic cleaner would do the trick. But if it were to remove the zinc coating of all the components, it would be bare metal and rust up pretty quickly again.



I hope this helps understanding the caps vent system.

Larry
 
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