I need some help from the shovelhead gods here.

Little about the bike:
1977 FXE
S&S shorty super carb
Intermediate jet: 27
Main jet: 70
Stock engine 74ci
The tank is clean, the inner tank filter is clean, the in-line filter is clean. There is no trash or obstructions from the tank to the carb.

The problem:
The bike will run fine till it gets to half tank. Then the fuel filter will run dry and the bike will cut out then die. If I blow in the tank, it will refill the filter, and run until the filter drains empty again. It will continue to do that until I fill the tank back full again. Then it runs fine until there is only a half a tank in it again. I've pulled the tank and filter twice, and there's nothing in it. The venting valve in the gas cap is working like it should. The tank is building pressure through out the run. I'm stumped. I'm open to all suggestions please.

Thanks in advance from my son and I.
Ricky

 

The tank is building pressure through out the run .... Pressure? When you release/open the gas cap you hear pressure or are you hearing vacuum? ( the tank sucking ) I'd say you have a vent problem. Do you have "dual tanks"? A single gas cap would lead me to believe that your cap ( contrary to your assertion isn't venting.

 

any chance you have your fuel house routed between the cylinders and it gets the hose to hot and it Vapor Locks ? S&S supplied an actual accordian type cover to go over the fuel hose on their Super E's because of that problem. Just an idea.

 

Yep that's a possibility also

 

I can suck air through the vent in the gas cap (from the back side) but can not blow air through it. The tank is defiantly building pressure. When I remove the gas cap off, you can feel and hear the air blow pass the seal. I've taken the petcock off and it is clear of any obstruction too.

Yes, the fuel line IS routed through the cylinders, and no, there's no additional protection on the lines. Could that be all there is to it? What do I need to fix it? And where can I find it?

 

Is it the stock tank? Any internal or external tank venting that is blocked off or obstructed? Replace the cap to be sure, or run it loose and see if that fixes the problem. I'm thinking flakey vent mechanism in the cap. YD

 

Vented gas cap,(right side) not working correctly.
Scott

 

"UPDATE:"

Seems that removing the inline glass filter and wrapping the line with a heat shield worked! Thanks everyone for the help!