Subframe tank vent routing

Gezwindespoed · Dec 19, 2014

Can anybody make a picture of their vent tube routing. My problem is that is if the vent tube is going all the way to the front tank vent, you will end up with fuel in the vent tube which blocks air when refueling (so fill goes even slower). Now i have a small tube as vent which I block off after fill up and open up after consuming half of the front tank. Then fuel will not get into the breather tube. This will work when not in a hurry, but will be a pain halfway durring a special stage on a rally (March 2015).

Rensho · Dec 19, 2014

I the vent line along the seat rail, into the airbox/fuel pump connection lines, along the frame and up to the gas cap.

Since you can never fill the subtank to the point where fuel is pushed into the vent line, I don't see how you end up with fuel blocking ventilation.
I can see fuel bouncing around and into the vent line, but most of that should also drain back out or evaporate.

I do agree the fill is slow, and a little painful. I use a filter sock, so it is even worse.

I have filled the subtank via opening the screw plug on the side. That works well. I was careful to open and close it.
Maybe a good way around this is to tap that plug, and put in some type of air bleed that opens and closes easily.
People are very touchy about that not being used as a fill port. I had read very early on that it was put there for that purpose.

I think the slow fill has mostly to do with the small tube connection between the two tanks.

akshun · Dec 21, 2014

How quickly do you need to refuel? It seems like a long time when doing it but it really is only a few minutes. My breather line runs along the seat rail then along the frame under the middle of the front tank and joins the filler cap breather line. It does fill slowly but isn't that much of a hinderance to me. There is no way i would be messing with any plugs on this tank, it was hard enough getting the thing to hold fuel in the first place, ha ha!

Gezwindespoed · Dec 21, 2014

Thanks for the replies. I can fill both tank till fuel comes out of the subframe tank vent hole (it is lower than the highest point of the main tank). When riding like that it is likely that fuel enters the vent line. Maybe i should just time it to get a objective result. Filling both tanks from almost empty takes about 6min. On my last rally you had 15min to fuel up eat something and repair if applicable. If fueling already takes half of that eating should be really quick.

Edit: Maybe filling up is even slower in my case because I have a safari pumphousing adapter and not the 70-degree one.

jon andersson · Dec 21, 2014

Shouldn't matter if fuel go into the vent line. It will be sucked back when the fuel level get lower.

Subframe tank vent routing

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