Changing all in tank hoses, how to handle vent/charcoal system

New day, new question on my 60K mile R1100RS maintenance project.

I've pulled the tank and am replacing all fuel lines along with the filter. I'm also trying to figure out how to deal with the evap system which consists of the two vent lines coming out of the tank and into the charcoal canister system. The previous owner already eliminated the canister and external vent tubes. He left me with the 2 vent lines dangling out of the tank and draining any excess gas or vapor to the air/street.

https://goo.gl/photos/BCzWnLHGUzWs5WhR6

That is the neck of my filler tube. It looks like one of the vent tubes is simply an overflow drain from the inside of the tank, and the other tube drains any overflow from the neck during filling.

Are there any established techniques to simplify this system? It seems like I need some kind of simple vent to allow for expansion/contraction with temperature changes. Additionally, I've heard of people trimming this tube back to allow for a more proper fill of the tank.

Any suggestions?

As you surmised, one drains spillage and (importantly) rainwater. That hose should be routed through the tank, out the fuel plate, along the right side, and to the ground near the right footpeg.

The other hose is for air expansion/entry. It was routed through the charcoal canister system (which some of us still have) to filter the air and recover vapor. That hose should also be routed in the same manner but should have its end trimmed at a 45 degree angle, with the angle toward the rear of the bike so that rainwater doesn't get drawn into the tank during an extended ride in the rain.

drj434343 said:

Additionally, I've heard of people trimming this tube back to allow for a more proper fill of the tank.

Click to expand...

Roger is correct about the hoses. They cannot be "simplified," given their different purposes. In addition to handling temperature-driven pressure changes, the tank vent allows air to enter the tank to replace the fuel that is removed by the fuel pump (the most important function of the vent -- without it the bike will eventually stumble/stall).

The hoses cannot be trimmed to change the fill level. The metal neck of the filler can be drilled to raise the fill level. If you have a charcoal canister (you said don't) raising the fill level can lead to flooding of the canister. If the canister is missing, there is the potential for overflow of the tank when filled to the brim on hot days as the ~55F fuel from the underground tank heats up.