Fuel tank vents and pop off

[N3vrSat1sfied]

Let’s talk fuel tank vents.

The factory Yamaha ones are one way but with a pop off. The aftermarket seem to never pop off and allowing the tank to build pressure past the needle and seat causing fuel to flood the engine.

This year with my skis on the dock I’ve noticed this with two different engines, different carbs, different tanks etc.

What’s the consensus, just use the oem fuel tank vents? Or do I have some other issues like weak springs? I did check pop off both times and it has been good. Last time I replaced the tank vent and put new springs on and didn’t have an issue afterwards.


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[Kohldanielzimmer]

Agree with your assessment.

OEM Yamaha have a threshold after which they will vent (rather than just let air into the tankl).

Seems like the aftermarket ones are ONLY a 1 way valve.

Yamaha ones are probably designed to work in conjunction with stock pop off levels (~50) so even OEM 1-way can trap enough tank pressure to over power the needle/seat with lower pop offs (not scientific but under 25 seems to be more prone to this issue).

Oem Yamaha is around 75 $ new so that’s a factor.

 

[beerdart]

Tank PSI can never exceed RVP of the fuel. Summer around 7 Winter around 9.

 

[kevbo]

An OEM vent valve is good if the popoff isn't too low. Any negative pressure will really mess up the way it runs. I like to use a water catch can and leave the tank free to breath.