fuel cap not venting

[jambretta]

I resurrected a CB77 that was sitting for 35 years. I found that the fuel cap does not vent air. I replaced the rotted cork with a rubber gasket (From Classic Honda Restorations). The air breather holes in metal parts that are visible are both clear. I felt in there with a drill bit and could feel some kind of membrane after the 2nd hole.

I was desperate, so I drilled a very small hole through the top of the cap metal (3/72 inch) as a temporary fix. I can seal it later if I solve the problem. I'm sure it will leak if the tank is 3/4 or more full and sloshing around.

What is the likely cause of this blockage? Was there some kind of breather channel cut into the original cork that my rubber gasket does not have? Is there something clogged in that membrane? I just don't see where air can get in when the cap is on tight, with a rubber seal.

Thanks,

Pelayo
Oakland, CA

[cadman]

The cap doesn't have to vent very much air. Fuel level goes down very slowly. Has it fuel starved when you ride it because of vacuum in the tank??

[jambretta]

Yes, although in combination with rust flakes in the petcock. Lack of airflow is pretty noticeable though. When I take the cap off after running the bike, there is a very audible "sssssssss" of air. I also have clear fuel lines so I can see the air bubble form sometimes due to the vacuum, then it all rushes once I open the cap.

https://plus.google.com/photos/11673619 ... 7601740916

[Goodysnap]

This may help you,

http://www.honda305.com/forums/anatomy- ... ht=anatomy

Nice pics, looks like your making progress.

If you already drilled a hole through the top you may just get a new/used cap

Goody

[jambretta]

Thanks so much. I searched the forum a few times, but used the term "fuel cap."

Pelayo

This may help you,

http://www.honda305.com/forums/anatomy- ... ht=anatomy

Nice pics, looks like your making progress.

If you already drilled a hole through the top you may just get a new/used cap

Goody