Fuel tank vents and pop off

N3vrSat1sfied

N3vrSat1sfied

Military Member
Location
Fort Worth, TX
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

Kohldanielzimmer

Sierra Nevada Runoff Rider
Site Supporter
Location
Ahwahnee, CA
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.
 
kevbo

kevbo

Location
dfw
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.
 
mrfist9

mrfist9

Location
ATL
I'd like to think I'm pretty well versed in this. I played with these a bunch.

The black and clear little check valves everyone runs, Jetmaniac sells them as well as others. Mcmaster sells them.

They're OEM on all the 90s seadoos.

On the seadoos they run a different setup though. they have 1 line out of the tank to a tee. The breather (this same 1 way valve everyone uses) goes from the tee to typically right under the hood. Then just under the bond line typically they have a bleed off valve at the other tee port, it bleeds off at ~5-10 psi or so.

The wonder of that setup is when you have it all right, man they start like nothing else. Happy 1 click starts always EVERY time.

I run that valve for the same reason others have mentioned in all my skis.... Cost the OEM is cost prohibitive.. I also don't believe it to reliably work as a bleed off.

I don't get the dreamy reliable 1 click starts, nor do I let my skis bake in the sun ever, my stuff all lives indoors not does it live on a slip or anything like that and I've never had flooding issues. Even on skis running lowlowlow pop off. Trade off I'm willing to make for the $2.50 those things cost. First mod for me on any ski.
 
WFO Speedracer

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
mrfist9 said:
I'd like to think I'm pretty well versed in this. I played with these a bunch.

The black and clear little check valves everyone runs, Jetmaniac sells them as well as others. Mcmaster sells them.

They're OEM on all the 90s seadoos.

On the seadoos they run a different setup though. they have 1 line out of the tank to a tee. The breather (this same 1 way valve everyone uses) goes from the tee to typically right under the hood. Then just under the bond line typically they have a bleed off valve at the other tee port, it bleeds off at ~5-10 psi or so.

The wonder of that setup is when you have it all right, man they start like nothing else. Happy 1 click starts always EVERY time.

I run that valve for the same reason others have mentioned in all my skis.... Cost the OEM is cost prohibitive.. I also don't believe it to reliably work as a bleed off.

I don't get the dreamy reliable 1 click starts, nor do I let my skis bake in the sun ever, my stuff all lives indoors not does it live on a slip or anything like that and I've never had flooding issues. Even on skis running lowlowlow pop off. Trade off I'm willing to make for the $2.50 those things cost. First mod for me on any ski.
Click to expand...
The only problem with the Seadoo setup is dirtdobbers like to stop up the one way valves, I have had to replace a lot of them in the past few years because of this.

I don't think the one way valves have anything with Seadoos starting the way they do, it has more to do with them being rotary valve engines and on the 787 DC CDI ignition, so the spark is there ready to go if the battery is hot.
 
mrfist9

mrfist9

Location
ATL
WFO Speedracer said:
The only problem with the Seadoo setup is dirtdobbers like to stop up the one way valves, I have had to replace a lot of them in the past few years because of this.

I don't think the one way valves have anything with Seadoos starting the way they do, it has more to do with them being rotary valve engines and on the 787 DC CDI ignition, so the spark is there ready to go if the battery is hot.
Click to expand...
Ehhhhhh they all ran awesome for me! 951 include dirt dobber nest gotta be a 20 year service haha
 
kevbo

kevbo

Location
dfw
The only problem I ever had with tank pressure was when I installed a primer. It filled the engine full of gasoline sitting on the trailer for a week., Thats when I started using a water trap and fully venting the tank. Over the years I had two failures caused by the vent valves in each direction. All you have to do with a water trap is check and drain it before each outing.
 
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