This came up in another thread, but I figured I would post it here. I have a Davis crawler, with a trenching attachment. It has a Wisconsin TJD engine, which is a two cylinder, air cooled engine. It drive a hydraulic pump, which in turn provides power to the drive axle. While it ran a few years ago, it currently doesn't. Over the years and a couple of big moves, the magneto and carb have been misplaced. I go back and forth on trying to repair the engine that's in it, or repowering it with something else. I've seen a few single cylinder diesel engines that might work out. Every once in a while I get tempted to just sell it as is, but so far I've been able to resist the urge. I like tracked equipment, and this is small enough that I don't have to drag out the forklift and 3/4" impact wrench to work on it.
In any case, here's a bad cell phone picture.