Soak in Gasoline for a little while to stretch it a bit and get it just right.
As others have said, at first the Rubber is too short and not very attached.
If you force it on as it is, it will bite and overflow all over the place.
It is recommended to soak the packings in Gasoline for a little while before use so that the packings will stretch nicely.
p.s. If you soak it too long, it will grow too long and you will not be able to get into it, so if it grows too long, let it dry for a while.

