I recently got a 1987 CBR600. The previous owner said that it leaked gas while running when he had last rode it more than 6 months prior. I cleaned the carbs and it starts now, but it leaks (dumps) fuel out of the AVCV. I don't know what that is or what is causing it. It is a round plastic CA Smog part I think located next to the PCV. Any help would be greatly appreciated.

Thank you

 

Air vent control valve which is a CA smog part ( as you stated ). Factory manual only has a very small routing diagram that is hard to read. There are a series of small vacuum/air lines, one set goes to the suction side of the carbs, one set goes to the engine side of the carbs and one goes to the canister. Funny that you have fuel in it as it should only have air. I would trace and disconnect one hose at a time and check for fuel leaks to narrow down where the leak is coming from. I suspect that maybe one of the diaphrams has ruptured in one of the carbs allowing fuel to get where fuel should not be.
How does the bike run? Good ,bad, what?
I have an '88 with CA smog stuff on it, but never had a problem with it. There are a lot of penetrations that all those hoses plug into which can cause all kinds of vacuum leaks if not properly connected. This will definitely cause performance issues. I took a pic of the diagram for you . I hope it helps. Good luck!

 

Thank you, it turned out to be a stuck float valve that was causing the carb to flood and that just happens to be the low point that it comes out of. After replacing the valve it ran good enough to ride. I never got the bike to run right and I eventually sold it, but I though I would put an answer for the next person who has this problem.

 

HAHA he said penetration...

 

Yeah, yeah,mmm,mmmm,mmmm,penetration!

 

HAHA Oh Dear