3hp Lightwin air-cap gasket

Hello, and nice to be here again after longer break. I have spent nice summer with my Evinrude 3hp, and it wants to start almost every time right on the first pull. Few days ago i noticed small fuel leak from the air vent cap. During my engine rebuild, i put new gasket to the fuel cap, and this is not leak. But small leak is coming through the air vent on the fuel cap, when fuel tank is full and engine is tilted up, but not when engine is normal driving position. I wonder if anyone have idea, is this air-vent gasket possible to change, and how it will happen? i have already kept the fuel cap in my hands and wonder, but i really have no idea how the small screw should be come off the cap?
I have made many nice trips during this summer, and engine works really good and economically, fuel consumption little over 0.26 gallon /hour.

The cap was not made to be able to dis-assemble or repair. As you can see, the vent screw is swaged on the end. Of course, that does not mean it can't be done with a little bit of creativity and imagination.

Yes really looks this for my eyes too, thank you for answer. And i really not want to do anything which could change the look of the original fuel-cap. This is not too big problem, usually i fill the tank while motor is on own stand, then i put motor to boat and lower the boat to the sea. And during that moment, i need keep the motor tilted up with full tank. I do have another fuel cap from parts-motor, but maybe the situation is same with that.

Welcome again and good to hear from our friend in Finland. What I do here is to remove by cutting off the problem vent gasket and install instead, an o-ring that can be stretched into place. This has been a great fix for all my motors that use this type of cap. Just look for the perfect size o-ring. Take care and yes....I have learned from you too.

Thank you very much timguy for telling about o-ring. I will try this. Now i need to wait about one week, before i can work with the motor, since i am now my city home.