In response to buying military gensets, I wouldn’t. I have owned quite a few of them and my view is they take a really good genset and make it so complex its hard to work on let alone get parts for it. The wiring is usually the problem, very complex.
I purchased a [commercial] 6.5 Kubota last year and it is a super gen set. I run it on Bio Diesel and it cost about 10 cents per hr to run. One good place to look for these is the Light Towers  web site. Check tool rental places for sales. Remove the gen set and use the trailer for tools or a Bug Out Trailer.
Here in the Midwest, the Purple Wave auction site  has them fairly often. Recently a Kubota 6.5 sold for under $500. Stay simple when it comes to gensets. I have owned two of the Chinese Diesel gen sets and I do not recommended them. I have a 20 KW Detroit Diesel genset I run my sawmill with. These are excellent, very robust and inexpensive to work on and operate. The prices on these are going up though. I paid $2,000 for mine and it may be the best generator I have owned. I currently have seven gensets. For small ones, I recommend that folks go with the Kubota. – Surplus Jim
In response to today’s advice on surplus generators I’d like to share my experience with them to warn others. Over four months ago I purchased a surplus diesel 1986 3 KW Onan generator from GovLiquidation.com  for emergency use in my house. I spent $500 and five hours of my time to get it but since the thing only had 120 hours on the meter and was built like a tank, I thought that it was worth the investment. I bought it fully expecting to spend couple of hundred dollars on a tune up to get it in working shape. But the thing is over 20 years old and did not start the way it was supposed to.
My local small engine repair place that constantly repairs similar civilian devices started having trouble with it from the beginning. They told me that there is a short somewhere in the wiring but since all the wires are white, the manual that I downloaded and printed off the web was no help. They said that they would have to rewire the entire thing and it would cost over $1,000.
Next I tried the “local” Onan service center (100 miles away). They had no clue about it. Apparently Onan keeps their military and civilian models quite different by design and model numbers so the rep couldn’t even accept it for service or give me any parts information.
After that I took it to an auto repair shop that specializes in electric repairs. So far they have been able to identify that one of the panels had burned out and needs replacement but they have been having trouble finding the replacement panel. Currently they are trying to figure out a way to adapt a part from a different generator to make it work. The good news was that I knew I was in a friendly place when I recognized a guy from my rifle range and another guy who got excited when he saw a mil surplus generator and asked if it can be buried. Now I have a good feeling about the guys working on it.
Overall I would not recommend buying similar items unless you have the knowledge to do all the repairs yourself or unless you know a local repair shop that is accustomed to unusual projects. It has been four months and it is still a work in progress with no official estimate on the cost of repair or even if the repair is possible. Sincerely, – B.G.