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.
I tried quite a bit; I'm a tool tech in a rental center, it's my job to go over these tools cleaning filters, assessing damage, and completing repairs.
This one's just a PITA.