Venting Diy subtank

Interesting question. I have a 70-degrees subframe tank - let me know if I can supply with you with pictures, measurements, or make experiments on it.

Make sure to remove the one way valve in the fuel cap. If not it will not level out between the tanks.

Jusaberg said:

Thanks for the reply Tourist is your subtank vent a one way valve or
Straight though? I guessing the angle
Of the bike and momentum in use may push fuel back in to subtank
And clear vent.
Does your vent line fill up to main tank height/full to the filler cap?

Click to expand...

No idea Haha. I'll have a look. The bike's not stored where I live atm; I'm planning on doing some nuts and bolts this weekend and will take pictures and take a look at the fuel routing and see if I can't build an understanding

There shouldn't be any one way valves to the subtank as air (and fuel) must be able to move both ways to fill the tank and deplete it. And yes, some fuel will go into the line when you top up the system but gravity and two way communication through the vent will drain it eventually when the level comes down.

I made my own subtank but I wasn't as lucky as you as mine was sweating fuel from the two highpoints at the back. So I was lucky to be one of the last to order a 70 degree tank.

Re-reading your first post again.. I did abit different vent routing so I have no lo-points. I can take pictures later but I routed my vent line on top of the air filter. But eventually I think your level in the subtank will level out as the pressure difference will suck out the fuel in the vent line.