They are probably just putting a 4 stroke snowmobile engine in these.
I have always thought that Yamaha was the best of the Japanese manufacturers vs. Honda, Suzuki, Kawasaki.
They are incredibly reliable well engineered machines.
Honda small engines are good, too. I have had a Honda lawnmower for over fifteen years and I’ve never had to do anything to the engine other than gas it up and change the oil every other summer or so. It just fires up and works.
I remember all the crappy mowers my dad when through trying to find one that would last, and they had all sorts of problems.
Honda outboard motors are also excellent.
Some of the 2 cycle engines they put into snowmobiles are hard to kill. Loved that I didn’t have to mix oil and gas, separate tanks for both.