Couldn't find a photo of one to tell. Mine fits very loose and rattles and seems to leak oil when running. So a gasket would seem to be required. But can't find one that the vendors sell or confirmation that one is needed.
I can make one on my own out of cork material, but is one standard?
No gasket on the cap. Just spread the metal out so it fits tight. At the top of the ring that slides into the casting there should be metal screening, maybe yours is missing? If you got oil coming out at least you know you are getting oil to front! Or you have a lot of piston blow by.
You mean the cap you remove to put oil in the engine? (Your mentioning the generator throws me off here)
The round part of the fill cap that slides into the engine has a split in it. If you take a plier and slightly dog-ear a small corner on one side of the split, it will interfere enough with the fit to keep the cap tight and not rattle. There is no gasket needed or even possible. The cap is also the breather for the engine, so some oil blow-by is always going to occur.
An accessory some people add is a chain hidden inside the cap to keep it from getting lost.
Would hate it if that chain got into the timing/generator gear. I guess the moral of the story is; use a short chain. ;O)
It's not uncommon for people to stuff a piece of "Chore Girl" up inside of it if it blows too much oil out of it. Just make sure it won't come back out.
Chore Girl.....it's a wonder they can even say that anymore.
What is Chore Girl? Sounds like someone I need to meet!
They make Chore Boy too. I think "Girl" is copper and "Boy" is copper plated steel. People who shoot cast lead bullets recommend "Girl" for cleaning lead out of barrels. They always caution against "Boy" due to possible barrel damage. I prefer a bullet .002" oversize and don't worry about leading to start with.