Help! Carb/tank problem

[Hackmachinist]

Last week I bought a 1974 CB350F from a friend. It's a beautiful bike and seems to run very well. I took it for its first long ride yesterday and after about an hour of riding I lost fuel and the bike died. The carburetor on the far right was pissing fuel from the drain below. Does this sound like a stuck float? Or would this have something to do with the fuel tank not being vented? The original fuel neck was cut off and an aftermarket flat cap Was installed but it is not vented. It is the push in type usually found on a boat. Please let me know if you have any ideas! Thank you for all your help!

Aaron

 

[carnivorous chicken]

If gas was gushing out of the overflow tube on one carb, then it's certainly a stuck float or a bad float valve -- something could have also found its way to jam the valve so it doesn't close -- does it have an inline fuel filter, or do you know that the petcock filter(s) are in good shape? Could also potentially be a bad float.

You wouldn't have been able to ride for an hour if the cap wasn't vented somehow -- you'd burn the fuel in the carbs and they just wouldn't refill, or they wouldn't refill quickly enough to keep you going at more than about idle. If you rode around for an hour, I'm guessing that there is some kind of venting happening in that cap.

Regardless, doesn't sound like your fuel pissing out of your carb is venting. Give that carb a light tap or two with a rubber mallet, and if that doesn't do it pull the bowl and check your float and valve. If it's the far right carb (#4), that is the easiest float bowl to pull because the starter cover isn't in the way (and it's on the outside). A z-shaped Phillips or a socket with a Phillips attachment will do the trick.

 

[Hackmachinist]

That does make sense about the carb . It does have an inline filter but maybe it needs changing while I'm down there.
The reason I questioned if the tank was vented was the amount of pressure it is under after riding. Gas will burst from the tank when I remove the cap . Enough pressure that it splashes on to the tank.

 

[carnivorous chicken]

That's a little nutso, but like I said, you wouldn't be able to ride for an hour unless your tank was venting somewhat. The overflow isn't from that, but you could always try riding around with the cap unscrewed a little, and look for a way to vent it.

 

[Hackmachinist]

Thanks for you help! I will let you know if anything happens