Robbins Power Bee motor. Master jumping jack rammer tamper.
When it is running right, sounds like a large loud swarm of bees.
Early to Mid 70's to mid 80's ground pounding technology.
I have one just like it, still will scream right along.
Down sides, no muffler, can't hear yourself think when it is running, neither can anyone else anywhere close.
No clutch, so when it is running it will be moving up and down.
Parts are getting hard to find.
Did it actually come without any cooling shroud? I understand the noise factor(OSHA will be calling them soon ... disconnected #) as 2T engines can sound like hornets/wasps(more like hornets) when buzzing along.
Rented a 2T post hole digger that was geared to start digging the moment the engine started. Took 3 of us brothers to handle that monster. Especially digging into the 'dobe' soil in NorCal. Just took some time travel back to the 1970s when all brothers were still kicking. And Ma and Pa. Coulda woulda shoulda...
That picture above is exactly what they looked like OEM from the factory, no shrouds around the motor.
I will take a couple pictures of mine as soon as I get over to my sons place where it is.
If OSHA calls, it won't make any difference, you will never hear the phone ring, phone on vibrate, still no good cause they shake so much you won't feel the vibrations either.
They are going to have to show up in person and poke your arm to get your attention to turn it off, then if they talk loud enough you may be able to hear them.
If you have been running it for a couple hours before they get there, if you want to hear what they say you have to read their lips. But do not fear if you don't read lips, they will write it all down for you to read.