I've had a 835 and a 838 for a few years as chain saws. The engines run nice and should be good in a model airplane.

I have a couple McCulloch weed whackers converted which work nice as model airplane engines and the chainsaws have even better timing.

The saws have a plastic case with a engine unit that is easily removeable. The carb is of generous size with dual needles, so should not need replacement.

I have found that the engines really wake up to take all the baffles out of the muffler.