International layover at Narita with only carry-on, different terminals & separate tickets: is 2h40min enough time?

Hi,

I will be arriving in Narita at 4:40 pm in terminal 2 with Japan Airlines with US passport. Then I have a flight to Busan in Terminal 1 with Korean Air at 7:20 pm. Those are separate tickets.

I will only have carry on (one backpack) so I won’t be checking in any bags. I’m young and don’t have mobility issues.

My understanding is that I don’t have to pass through immigration and I can go straight to connection flight after passing through security. Is this right?

Historically the Japan airlines flight tends to be on-time but obviously can’t predict. Flight from Narita is relatively cheap so it wouldn’t hurt much loss if I miss the flight.

Would this be enough time? Thanks!