Tank Breather

[Mittzy]

G'Day,
Can someone tell me if the fuel cap acts as a breather for allowing air to replace the fuel as it is used up?
I ask this cos when i fill to FULL then BLAT down the road I can get a spray of fuel from the non genuine filler cap. I want to know if I make a gasket for it to seal i wont be creating a vacuum as the fuel makes its way out the exhaust to give me joy.
Pic of cap assembly

 

[barbagris]

There should be vent tubes close to the filler built into in the tank As long as those still breathe you should be OK.

Hard for me to tell from the photos haw the flow works - but another option MIGHT be to drill that top inner face so the fuel can drip down and out of the vent tubes (there for that purpose)

The aftermarket fillers I have seen often have an o-ring in the thread

 

[1olbull]

G'Day,
Can someone tell me if the fuel cap acts as a breather for allowing air to replace the fuel as it is used up?
I ask this cos when i fill to FULL then BLAT down the road I can get a spray of fuel from the non genuine filler cap. I want to know if I make a gasket for it to seal i wont be creating a vacuum as the fuel makes its way out the exhaust to give me joy.
Pic of cap assembly

Tony,
Hopefully you are not filling above that drilled screen shown in your second pix?
I have the same cap & never an issue after thousands of miles between 40 and 117 degrees Fahrenheit.

 

[barbagris]

Ah but it's upside down fuel in OZ!

 

[Mike Rocket]

I have filled mine a bit above the drilled plate and parked in the sun for 1/2 hour or so and when I came back the fuel had expanded and ejected itself out of the vent tube by the starter motor and the battery vent pipe. So it looks like the fuel cap can seal fully as the tank is vented via this pipe.

 

[WyldCFH]

Mine is a different style but has gaskets from the manufacturer and no issues so far.

 

[Mike Rocket]

I have filled mine a bit above the drilled plate and parked in the sun for 1/2 hour or so and when I came back the fuel had expanded and ejected itself out of the vent tube by the starter motor and the battery vent pipe. So it looks like the fuel cap can seal fully as the tank is vented via this pipe.

Mine is a factory standard cap.

 

[Rocket Scientist]

One line vents the tank, the other drains the recessed area around the cap in the event of an over fill.

 

[Claviger]

Can easily do a check on the vent, try blowing into with the cap off, should be very easy. Vent line runs under the tank along the left side and comes out under the battery box somewhere.

 

[warp9.9]

two lines but at different levels in the ring of the tank Yellow arrow below runs to the rear port on the tank and then down to the rollover valve. it is higher off the tank then the moisture drain in green (circled on the left) which is flared to collect all the stuff you do not want in your tank.

Hope this helps