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Hey guys,

I bought a '92 CBR600f2 with about 40,000 miles on it a few months ago. I knew there would be some problems with it being that it was an old bike but I am pretty mechanically inclined and haven't had many problems I couldn't figure out on my past cars and even an old motorcycle I owned. With this said I am now confused.

The other day I had fuel leak out my cap and assumed that although I filled it below the neck of the filler cap, perhaps that was still too much and caused gas to spill over through the cap. The next time I filled it up I put even less in it and the same problem. I woke up this morning and went out to my bike and the concrete was saturated with gas in about a 3 foot diameter around the bike and it was slowly coming out the fuel cap. Needless to say this has already ruined my paint. When I open the cap I can see that the gas is still well below the line but it appears that gas is coming up the overflow hole and then spilling out. As soon as I open it it begins to drain down the hole and disappears pretty quickly but as soon as I close it again and the filler hole gets sealed it does it all over again. If i put my ear near the tank i can even hear it begin to bubble just before it does that.

The bike runs great and this problem doesn't present itself until some time after sitting after riding it and only when it sits in the heat (which is pretty much during the entire day because I live in FL). Any ideas on what is causing this or how to fix it?
 

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Hey guys,

I bought a '92 CBR600f2 with about 40,000 miles on it a few months ago. I knew there would be some problems with it being that it was an old bike but I am pretty mechanically inclined and haven't had many problems I couldn't figure out on my past cars and even an old motorcycle I owned. With this said I am now confused.

The other day I had fuel leak out my cap and assumed that although I filled it below the neck of the filler cap, perhaps that was still too much and caused gas to spill over through the cap. The next time I filled it up I put even less in it and the same problem. I woke up this morning and went out to my bike and the concrete was saturated with gas in about a 3 foot diameter around the bike and it was slowly coming out the fuel cap. Needless to say this has already ruined my paint. When I open the cap I can see that the gas is still well below the line but it appears that gas is coming up the overflow hole and then spilling out. As soon as I open it it begins to drain down the hole and disappears pretty quickly but as soon as I close it again and the filler hole gets sealed it does it all over again. If i put my ear near the tank i can even hear it begin to bubble just before it does that.

The bike runs great and this problem doesn't present itself until some time after sitting after riding it and only when it sits in the heat (which is pretty much during the entire day because I live in FL). Any ideas on what is causing this or how to fix it?
Sounds like the breather is blocked.
 

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Should have an overflow pipe and a breather pipe, check that they're not blocked, tank needs to breath or else will create a vacuum. A pressure build up could be forcing the fuel out.
 
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