I beleive that is a very old air compressor and the tank is gone. It would be gas powered with a gen attached . The pulleys are still there but donot see the big pully that had a very large belt. I had something long ago looked like that. Mine you put gas in and cranked it with a wrap around the pully rope. That sucker would thump all day long. Maybe not but looks like it.
Naw but back in nom I had a buddy ask when he arrived where da girls at? I replied over there is a camel, he said naw. Week later went by he asked again, where be the women at round here? I said camel still over there, he said naw was not that hard up....Another week and he asked me so where da camel at? I said over there . Next day I asked how was camel ride? He said not so bad but rather had a woman. I stated well we just use the camel to ride to town where all the girls hang out instead of walking.
Definately not a tractor engine....looks like an overgrown maytag washing machine engine...would'nt think its a rotax with an autolite starter....maybe the starter is just a replacement for the original.