Topic: 1977 CB750k, I have a question about gas tank vacuum.

[Pielz]

I apologize if this has been posted and solved before, I couldn't find it so if anyone has a link, feel free to share it.

My main issue is, I took my bike down to fill it up and halfway down the hill I was riding down it sputtered and died like it was out of gas. Stopped in a parking lot and moved the bike around and there was still about a gallon of gas in there. Switched it to reserve and it started back up. Weird, I thought and drove it the other quarter mile to the gas station. When i removed the cap it made a vacuum sound like it was releasing pressure and immediately i realized what had happened. Does anyone know why it would be suddenly doing this? fuel lines are running as down-hill as possible and i don't have an inline fuel filter as i just sealed my tank and i no longer need it. So what gives? Is there something i can soak the fuel cap in to clean it? Or do i need to purchase a new or aftermarket one? Are there even aftermarket caps for these k7 tanks? It just started doing this, and had no problems before. Thanks in advance   

[jaytee-nz]

The fuel caps have a vent system within them to allow air in as the fuel level decreases. Sounds like yours is blocked - maybe as a result of your tank lining job ?

[Pielz]

Oh that's totally a possibility. Although I had the hole taped off and the cap was only used when cleaning the tank. Although, I guess it's possible that it's started rusting inside from the rust remover in the sealer kit. Do you know of anything I should do to fix it? Or know of a suitable replacement if it's better to just swap it out?

[BenelliSEI]

There is a stack of metal discs in there, with offset vent holes in each one. That act as a baffle to stop fuel sloshing out. As a temporary solution, just open the cap and drill into the first vent hole (plug the gas tank opening first). Keep punching up until the drill bit hits the solid feel of the chrome outer shell and stop. That will work for a while. Don’t over fill the tank and order a new one.