Hello Bill, welcome to the forum, glad you joined us
I know a few that have done a trike, and only one of a recumbent.
If you go to Spooky Tooth Cycles - Motorized Bicycles: Gas Powered and Electric Bikes - Home
they have a complete trike and also a trike conversion kit.
Here are some videos of the only recumbent bike that I know of
YouTube - Lifan test fire
YouTube - Riding home
YouTube - Another ride
I have seen many on You Tube with a weedeater set up...there are members here using weedeater motors but mostly friction drive. I do not know much about them.