What is this?

And spark plug replacement or valve adjustment would likely require removing it from the coach.

Onan 5500 or 6500 generator. Very easy to change brushes mounted that way.

Pogoil.

Onan Genset. Mounted sideways due to mounting in the front of the Motorhome. The pass side would be the actual "front" of the Genset. Doug

Okay, Most of the generators I've seen in motor homes are in a metal box so you don't see much of the mechanical parts.

Air filter is black box on the left with the two on-generator breakers below it.

wolfe10 wrote:
Electrical end of generator.

Yep, and it appears to have an hour meter at the top right.

Electrical end of generator.