After doing a bit of research myself, it looks very similar to the engine in a Kia K2400 or a Kia Ceres. Not something in the US, so maybe?
I went out to take some pictures for you guys tonight and found a Dataplate that Generac painted over. I tried very lightly to remove the paint, but I ended up taking off too much so I stopped. See the images below as well as a picture of the engine pump. Looks like a DOOWON pump?
Just to give you more of a back story, I bought this Genset and it sat in storage for about 7 years before I tried to use it. It had 10 hours on it from the factory and I ran it for about 30 Minutes before it started making a strange sound. I of course did a full Oil change before I ran it after sitting this long. About 30 seconds into it making a strange sound the engine shut down. I pulled the head and found that the exhaust valve dropped into one of the cylinders and caused one of the cylinders to break apart. The cylinder walls seem undamaged though so I think I got lucky. This was about 7 years ago. At the time I ordered all the parts I needed to fix the engine. I got busy and forgot about it. When I checked the parts I ordered, I found that they had only shipped half of them and that the company went bankrupt and kept my money. Ugh.
I finally have time for this and now all the parts are discontinued that I need. I am trying to find a piston, connecting rod, rod bearings, a valve, valve springs, and valve cotter pins.
Thanks for the help.