I'm scheming to swap a diesel engine into a motorcycle, primarily to run on alternate fuels (biodiesel and/or veggie oil). I realize that many here will think I'm a nutcase and that this is a crazy idea -- I'm used to that

I have a motorcycle license and a '79 Vespa P200E scooter which I've ridden rather infrequently over the last 5 years. Other than that, I'm a little clueless when it comes to makes/models of motorcycles.
So I'm looking for recommendations on standard/naked bikes that would be suitable. Something inexpensive from the 80's (or even late 70's), relatively plentiful so I can find parts for it, lightweight, and with plenty of room in the frame to make mounting the diesel engine a little easier. The engine I have in mind is a Deutz F1L-208 single-cylinder diesel, about 23" tall.
This has actually been done before -- my favorite example is the "Changzuki":
http://psychicworldusa.com/Diesel_Bike/Suzuki.html
If mine is slow and spews black smoke like that one, I will be very pleased

Anyway, recommendations on bikes that would be suitable conversion candidates are greatly appreciated.