rubber seal

[honda250xrider]

I have a problem with the rubber seal on a honda 250x. The seal is on the top part of the head and on the right side. I have had to put this seal back in 2 times because it will pop out of the head. does anyone have any idea what would cause this?

[Aceman]

Are you talking about the black plastic seal at the end of the cam?

[honda250xrider]

yes i am