[ukzx10r]

I purchased a quick release fuel cap for my bike and it seemed to fit ok.
Filled up with petrol and when i broke hard petrol was pouring out the overflow pipe.
Ive had these caps before with no issues so am i missing something here?
No fitting instructions came with it.
Tank has two small holes under the cap so i think petrol is running out of the tank breather hole into the drain hole?

 

[scout]

the cap is not sealing. Fuel injection is closed system. Make sure nothing is on the cap gasket. Overflow is for when filling the tank. If overflow is allowing fuel to spill when closed the the gasket is failing for some reason. check to make sure you have the right cap.

 

[ukzx10r]

the cap is not sealing. Fuel injection is closed system. Make sure nothing is on the cap gasket. Overflow is for when filling the tank. If overflow is allowing fuel to spill when closed the the gasket is failing for some reason. check to make sure you have the right cap.

I will check. There are 2 small holes in the top of the tank. Isnt one the breather hole for expansion?
As standard that hole has rubber washer and links to the cap to vent from what i can tell. With qr cap it just sits there open so i prrsumed petrol could come out of it?

 

[scout]

I will check. There are 2 small holes in the top of the tank. Isnt one the breather hole for expansion?
As standard that hole has rubber washer and links to the cap to vent from what i can tell. With qr cap it just sits there open so i prrsumed petrol could come out of it?

I checked the '11 g4 cap; the overfill exit hole is outside the cap gasket seat area. That is the only hole.

edit: after re-reading your original post about the two holes UNDER the cap, I checked my above oem cap and it has one hole under the cap BUT still inside the gasket area that must seat upon the top of the filler cap. Has to be same with your new cap but either the gasket is missing or wrong size. Hope this helps.

 

[ukzx10r]

I checked the '11 g4 cap; the overfill exit hole is outside the cap gasket seat area. That is the only hole.

edit: after re-reading your original post about the two holes UNDER the cap, I checked my above oem cap and it has one hole under the cap BUT still inside the gasket area that must seat upon the top of the filler cap. Has to be same with your new cap but either the gasket is missing or wrong size. Hope this helps.

When you open up the standard cap you can see a small vent hole on the right hand side which has a rubber seal.
But when you unbolt the cap there is an overflow hole underneath on the left hand side so it can drain when the bike is on the side stand.
I think my main seal isnt quite sealing on the quick release cap i have which i can solve with a thicker seal.
The issue i have is what do i do with the vent hole?
If i block it the tank will pressurise but if leave it surely fuel will leak out of it when the tank is full?
After market items seem to just come with a seal for the main refuling hole and nothing at all for the breather hole

 

[scout]

My read is your prob has to be the main gasket failing to seal. The over flow is outside that main seal and is simply to get rid of too much fuel at the fuel station. The 'breather' hole I have no understanding and not sure of the engineering involved so we'll need a tech guy here like Sky or one of the other guys.