Vent hose valve

Ducamok · Jun 2, 2022

The thing that the gas tank vent hose attaches to inside the tank- is it a one way valve or just a liquid blocker. Currently it doesn't stop air going either way and I wonder if that's right.

The bike stops running after about 5 minutes, then fires back up and works well until I stop for awhile. It usually quits right as I'm getting on the freeway and tries to kill me.

I'm looking for fuel problems.

2013 821 Std.
Rapidbike easy
No charcoal cannister

uncle brad · Jun 4, 2022

Not sure about the construction of that check valve but when the bike quits, does it take a short while before it will start or will it re-start immediately? IF that valve isn't working, you should be able to pop the filler cap and it should start immediately.

This is what i found in a maintenance manual for my 2016. If i'm reading things correctly, it appears as though that valve is a breather to allow flow in both directions. It may have a valve in it to prevent the contents of the tank from leaking out if the bike tips over.

The parts list identifies it as a 'BREATHER'

This post mentions the ability to blow back through the hose to the accompaniment of a farting sound. Intrigued yet?

https://hyperstrada.com/threads/tank-vacuum.2042/

Araitim · Jun 5, 2022

I like to say my bike "Moo's" like a cow. It's kind of funny and fun. I know alot of the hyper 821/939 do it. I believe that it make a suction noise when you open the cap. To verify if it's sucking or blowing you could take a match, place it next to the gas cap n open it. If it sucks the flame in then it was a vacuum, if not it was pressure built up.. JK DO NOT DO THIS!!! It was a JOKE.
I think it's pressure built up inside the tank. The reason I think this is because it Moo's more on hot days and gasoline creates more pressure when it's warmer(you can see evidence of this with a gas can filled for yard machines. They tend to bloat on hot days).

Vent hose valve

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