Vented fuel tank query.

[Adie Porter]

Hi Guys, im swapping out the carbs and airbox for a top tank and flatslides.
Fuel cap in the fake airbox cover.
What im interested in finding out is, do i need to vent the tank or just use a vented cap?
I am looking for the flush harley style push in to pop up filler cap. How much venting is needed if the carbs are sucking the fuel down, also im in a hot climate and the fuel can expand.

 

[MaxMidnight]

As long as the air pressure in the tank is the same as ambient I don't think it matters how you achieve this.

 

[Adie Porter]

I dont have to calculate what fuel is being sucked out and compensate with a particular dia of hole for air flow in? Am i looking too deeply into thia?

 

[MaxMidnight]

Am i looking too deeply into thia?

Possibly.

I doubt (but am happy to be proven wrong) that as long as the vent hole is (say) 1 - 2 mm that would be sufficient.
I doubt that the volume of fuel drawn even at full throttle is so big that a small hole will allow the ambient pressure to be maintained.

 

[Adie Porter]

Thanks for that MM.

 

[Fire-medic]

I used a small drill bit and got a rough measurement of the OEM gas tank vent dia. which is 0.8mm or 1/32".

 

[wayne billings]

Goood morning- What does one do about repairing or replacing the fuel cap rubber . thanks wayne b

 

[Fire-medic]

Goood morning- What does one do about repairing or replacing the fuel cap rubber . thanks wayne b

https://www.vmaxforum.net/threads/g...or-dry-rotted-or-cracked-gas-cap-seals.20337/

 

[wayne billings]

Fire-medic hello again . the gas cap on my '86 needs a rubber seal. I serviced the cap and is working well. I cannot locate a seal. thanks again and I hope you are doing well. wayne b. [email protected]