California fuel tank nozzle

[silas]

If you happen to have a California model or even just a CA tank, and the emissions cans and hoses happen to be missing, and you were wondering what to do about the nozzle in the front of the tank...

...do NOT plug it up.

It is a pressure release valve. It needs to stay open to allow the tank fumes to escape. Discovered today that quite a bit of pressure can build up if that nozzle is blocked—especially on a nearly empty tank. Luckily, my face wasn't hovering right over the cap when I opened it.

[FJmonkey]

If you happen to have a California model or even just a CA tank, and the emissions cans and hoses happen to be missing, and you were wondering what to do about the nozzle in the front of the tank...

...do NOT plug it up.

It is a pressure release valve. It needs to stay open to allow the tank fumes to escape. Discovered today that quite a bit of pressure can build up if that nozzle is blocked—especially on a nearly empty tank. Luckily, my face wasn't hovering right over the cap when I opened it.

Then what do the flapper in the cap valves do???

[AustinFJ]

If you happen to have a California model or even just a CA tank, and the emissions cans and hoses happen to be missing, and you were wondering what to do about the nozzle in the front of the tank...

...do NOT plug it up.

It is a pressure release valve. It needs to stay open to allow the tank fumes to escape. Discovered today that quite a bit of pressure can build up if that nozzle is blocked—especially on a nearly empty tank. Luckily, my face wasn't hovering right over the cap when I opened it.

Then what do the flapper in the cap valves do???

It let's air in as fuel is removed.   The idea with the CA bikes (well, all of them now-a-days) was to force any fuel vapor in the tank to go to the carbon canister and NOT release it to the atmosphere.

[FJmonkey]

It let's air in as fuel is removed.   The idea with the CA bikes (well, all of them now-a-days) was to force any fuel vapor in the tank to go to the carbon canister and NOT release it to the atmosphere.

I am not so sure about that, after a run when all is hot and I park it it sings. While in motion air is flowing keeping engine heat moving rearward. When stopped the heat is trapped under the tank. My can casters we're removed and the tank plugged years ago. I think the flappers work in both directions.

[silas]

The orange flappers in the cap are in the same circuit ahead of the nozzle in front. They appear to function as a venting valve. I'd have to tear everything back down again to be certain which way (and when) they control the flow. But since there are two flappers in the white plastic housing element, I'm assuming is a sort of switch... allowing air in to prevent a vacuum in the tank, and allowing excess fumes out to the emissions equipment.

My cap used to whistle too, until I tore it down and thoroughly cleaned every part. There was a lot of dry corrosion throughout the entire assembly. Used carb cleaner on the metals and WD40 on the plastics and rubber bits. The whistle must be the result of a partially plugged port or a leaking flapper seal.

[AustinFJ]

It let's air in as fuel is removed.   The idea with the CA bikes (well, all of them now-a-days) was to force any fuel vapor in the tank to go to the carbon canister and NOT release it to the atmosphere.

I am not so sure about that, after a run when all is hot and I park it it sings. While in motion air is flowing keeping engine heat moving rearward. When stopped the heat is trapped under the tank. My can casters we're removed and the tank plugged years ago. I think the flappers work in both directions.

If you plugged the normal vents in your tank, of course the flappers will sing.  They are giving way before the metal of the tank.   Doesn't mean they were meant to work that way.   
And think about it.  If you have a vent of fumes to atmosphere, why would you have (stock) charcoal canisters?  Doesn't make much sense.  The CA version even has a solenoid to close the vents for the carbs when the bike is off, so having a vent on the gas tank going directly to atmosphere, again, makes no sense.

[FJmonkey]

If you plugged the normal vents in your tank, of course the flappers will sing.  They are giving way before the metal of the tank.   Doesn't mean they were meant to work that way.   
And think about it.  If you have a vent of fumes to atmosphere, why would you have (stock) charcoal canisters?  Doesn't make much sense.  The CA version even has a solenoid to close the vents for the carbs when the bike is off, so having a vent on the gas tank going directly to atmosphere, again, makes no sense.

Not trying to be difficult, but other non-CA bikes sing as well. Maybe I'm missing something...

[AustinFJ]

If you plugged the normal vents in your tank, of course the flappers will sing.  They are giving way before the metal of the tank.   Doesn't mean they were meant to work that way.   
And think about it.  If you have a vent of fumes to atmosphere, why would you have (stock) charcoal canisters?  Doesn't make much sense.  The CA version even has a solenoid to close the vents for the carbs when the bike is off, so having a vent on the gas tank going directly to atmosphere, again, makes no sense.

Not trying to be difficult, but other non-CA bikes sing as well. Maybe I'm missing something...

Just free flow AWAY from your flapper valve.      No worries!  I do not believe the flapper valve is any different in the non-CA versions, just that it was used in them.   Mine is a CA version and in the 110 degree heat, my flapper has been known to sing as well.   All I was attempting to establish was that the flapper was not a 'vent-to-atmosphere' by design.  It might have indeed been made to allow venting 'out' into the canister system as well as 'in' to the tank, but I have difficulty believing it would have been used in the CA system if it did not function as previously described. 
I do not believe it was made to vent the tank to the atmosphere, that's all.  When it is singing, I believe it is not functioning correctly in that it is (most likely) venting fuel vapor to atmosphere. 

That's all I got. 

[silas]

Anyone know how non-CA tanks vent off fumes?

[Firehawk068]

Anyone know how non-CA tanks vent off fumes?

Directly to the atmosphere, via the flapper valves in the cap assembly..........Mine used to sing when the bike sat after being hot.
If they are singing, they are working properly........
In certain situations, like refueling while hot, while using my tankbag, the flapper valves wouldn't release pressure fast enough, and I would get fuel seeping up through the keyhole.
I have since removed the flapper valves, and have not had that problem since.

[silas]

So, the exit point is the keyhole?

[RichBaker]

Non-CA bikes have a hose that attaches to a tube off the back of the tank, it goes down to below the engine and drains any overflow, I've always assumed the fumes go out that....

[silas]

Non-CA bikes have a hose that attaches to a tube off the back of the tank, it goes down to below the engine and drains any overflow, I've always assumed the fumes go out that...

The CA tank has that overflow nozzle as well.

[RichBaker]

Never looked at a CA bike....  Maybe the GYSM has a section that explains the fume recovery system.  RTFM?

[AustinFJ]

Anyone know how non-CA tanks vent off fumes?

Directly to the atmosphere, via the flapper valves in the cap assembly..........Mine used to sing when the bike sat after being hot.
If they are singing, they are working properly........
In certain situations, like refueling while hot, while using my tankbag, the flapper valves wouldn't release pressure fast enough, and I would get fuel seeping up through the keyhole.
I have since removed the flapper valves, and have not had that problem since.

The valve was not made to vent fumes to the atmosphere.