Originally Posted by sailah
Originally Posted by hpsVFR
Another option would be to run the vent line into the main tank through the fuel filler cap. Any spew would just go into the tank. Routing the vent line to the front of the tank would prevent length problems when the filler cap hinged forward to open.
Not sure how I'd go about this. I want to keep that fuel cap vent open so that pressure can't build in the tank
I was thinking that you'd take your vent line from the sub-tank and run it underneath the main tank, all the way to the front, then up, over the top and to the filler cap. You'd have to modify the cap to accept the vent hose while retaining the water seal, and retaining proper cap vent operation. I was thinking something like a straight (not 90º!) barb fitting bolted/glued into a hole drilled all the way through the cap.
I don't know if your cap has enough space to drill a hole, install some sort of pipe/tube (to prevent fuel seepage, and retain a vapor-tight seal), and glue/weld/bolt a fitting on the top. That's a lot of stuff to put into a fairly small space, and this seems like the biggest challenge to what I've suggested.
On the positive side, you would retain all the original characteristics of the positive-pressure tank, and (hopefully) retain the action of the tank vent. Your sub-tank vent line would be above the max fuel level in places where it's exposed. Areas where it's below max fuel level could be protected fairly easily, for example by using fuel line as chafe gear.
You'd also obtain that awesome old-school race-bike look, with a fuel tank cap with a vent line loop sticking out the top.
I hope that clarifies what I'm thinking about, and good luck with it no matter how you end up dealing with it.