The OS LA series
I put an OS 46LA on my stick 40 trainer. My instructor and others recommended a plain bushing engine to start with. So far it has run great with a nice reliable low idle. I am on my third gallon of fuel and it needs very little adjustment and starts good. I know there are more powerful 40 size engines around and I plan to get a TT 46 pro for the Spadstick I am building but the LA has done what I wanted,provide reliable power for training.