1977 RD400 Fuel cap seal replacement

[X-Man]

So I got a new tank cap seal and I dont see how to get the new one on? My cap does not have the screws on it to disassemble. Do I just heat it up and stretch it over? Can anyone advise me?

[1976RD400C]

As I recall from one I did years ago, just stretch it on there and then seat it in place.

[X-Man]

Yeah I tried that after getting it hot in water but felt it was gonna rip. I guess I could always just get another seal if so?