I thought it was a ball and spring, not a stone.
I thought that was what I said, did not notice which way the arrow was. It is the only line so it must do both, obviously not with the same amount of pressure required.
It has to go through the canister both ways. When I said verify, I meant the ability to draw vacuum in through the canister and difficulty in blowing it out through the canister. When this valve on the line from canister to throttle body opens, engine vacuum could not only evacuate the canister but assist in opening the valve in the tank. How hard did you suck on the tank line?
My tank line is disconnected with a filter on line end. It still builds up pressure occasionally on hot days.
I guess I could pull the valve out and check exactly how it works, but it has been that way for 3 years with no harm. It would be different on a carb'd bike.