I noticed that when my bike gets tired, lays down for a nap, gas spills out of the gas tank vent lines. With our small gas tanks I would like to keep as much fuel as possible where it belongs. I heard that we can install a one way valve in the lines. Fuel stays in and air can enter and vent the tank. Has anyone done this mod ? Does it work as stated and where can I find these valves?

 

I don't let mine take naps![sm=noooo.gif]

 

Gas tanks will build pressure and also have negative pressure, I don't think a one way valve would be a very good idea. If you've got a plastic gas can, watch it when the temp changes. The one I have in the garage will suck the sides in when cold, but when it warms up it balloons out and doesn't even sit flat.

 

I know that "Tusk" makes them. "Gas Tank Vent Valve". Thought possibly someone on the forum has installed them and can give a report on how well they work.

 

I had one on my 650L. Not worth it IMHO. Like mentioned gas needs to breath both ways. My tank wouldexpand a little if sitting through temp changes. (I had an IMS plastic tank since the stock is steel & had an internal vent BTW).

 

What you need is a valve that closes when tilted past about45degrees sideways. Hmmm... maybe I should design something and sell it. Here's how you'd make it.....

You need an upward curved plastic tube with a stainless steel ball. On each end of the tube is a perpendicular air passage that the ball will block if it rolls to the end of the tube. The air passage tube connects to both ends.

Sooo... you would need a piece of 1/2" Polyethelene air tubing and a stainless steel ball small enough to fit inside it. The trick is designing end caps so the ball blocks the air flow when it at the end of the tube, but passes air at other times.

The other solution is atilt switch that closes a small solinoid valve blocking the vent hose. You would need to run connect to the battery with a fused wire to a normally open tilt switch. Then wire the normally open solinoid valve in a series with the switch. THen run a wire backtothe battery.

Option 1 is a all mechaincal solution... option 2 is a electrical solution.

 

ok say you put a valve on one or both of these lines...... the closest you can put them to the top of the line is right at the tank..... soooo that means that there is still going to be gas from the gas cap to the bottom of the tank, ( In the lines) then when you stand it up it will still dump out gas from that 6" or so of line..... right? not even worth time messin with.... just dont lay the bike down as much....

 

I'm not 100% sure on this, but I am fairly certain that the gas tank vent valve from Tusk (and many others) is not really a valve so much as it is just a cover of sorts. They are intended to be used as replacements for the long breather tubes that come out of the caps of most plastic tanks. Instead of having the long tube dangling that needs be tucked into some nook or cranny, you can replace it with a short tube that has the vent valve on top. Again, I could be off base on this, but I think in this case, the purpose of the vent valve is to prevent water and other stuff from getting into this short tube and directly into your gas. I don't think it seals in either direction. I think it's internals are more just a series of double-backs so the outside stuff doesn't have a direct shot in.

Here's a pic of what I am talking about. If you are referring to a different thing, then just ignore that whole paragraph.



I bought one of these to use on my KLX300R tank, but I haven't swapped it in yet.