In my opinion, any engine can be converted to spark ignition and gasoline. The questions is how much oil is needed, and whether or not the stock carb will be acceptable. I would use a Walbro where space and weight allow it. If the stock carb tune well a Walbro is not needed.

Liquid, I like to see a viscosity of >13cSt at 100°C. I would use a more robust oil, especially with a pipe.