I don't know the answeres to your ?
But I have a Stihl FS 110 R that sees a lot of use, From normal use around the house to cutting down small trees and bushes in the woods, It always fires right up and it is run for hours at a time only stopping to add fuel or line. I have no complaints I am going on two years and many many hours on it.
I'd Buy another one of these if something were to happen to mine or if I was looking to add another.
The 4 Mix motors are different, It took me a little to get used to it, when I first fired it up I was like whats wrong with it, didn't feel like a normal two stroke wacker, but this think is like a diesel compared to a gas motor tons of low end, and after a few tanks of fuel she loosened up and does spin up some more. I think this motor is a great wacker motor has the low end to cut brush and spins just right to wack the grass and weeds and it jusr doesn't get bogged down like a lot of others this thing keeps on pulling, I am glad I got the 110 it seems to be a great balance of power and weight