The cover for the airbox on this Honda generator hinges open to the left, but the frame rail is directly in front. The airbox is also bolted to the engine from inside (behind the filter).
I’ve throughly looked over this and there is no way to open that airbox unless you unbolt the engine from the frame, or perhaps modify the lid hinges with a saw so it doesn’t have to swing as far to come off.
What model generator is that? I love figuring out things like this, I’d be happy to dig around and see what I can find.
pretty sure it’s EP2200CX
multiple posts online of people bitching about the same problem, visually looks the same as well with the box being blocked by the framing.
https://www.manualslib.com/manual/677509/Honda-Ep2200cx.html?page=41#manual
page linked to the filter removal. 41
This one looks most promising.
So … yeah.
Edit: If you don’t have a second person, you can probably pull the engine back with a ratchet strap after unbolting the mentioned mounts.