Well, that was very informative! Thanks for the explanation.Riding lawn mowers popped over the 20 horsepower mark in the early 2000s..
They have always had larger ones but they became more mainstream. Briggs & Stratton single-cylinder overhead valve has dominated from around 95 on up. The most common riding lawn mower in existence is a 42 inch 2 Blade. The started out having a 12 to 15 horsepower engine and then they crank them up and most all them had at least 17 and the most powerful singles had 25 horsepower. You also had horizontally-opposed twins that had 12 and 14 horsepower but we're a twin flat head. Then for most of the mowers larger than 42 in which for a long time was most commonly at 48 but there were a couple of 44s. These almost always had a twin-engine. At first the Twins were horizontally-opposed L heads or Flathead Briggs but then they came out with their V-Twin. On the Kohler side Kohler had their Magnum engines which were a flat head opposed twin and then they came out with her between also. It's just as bad as the car manufacturers. They just copy each other and always make the same basic thing and every basic period.
I always complain that too many 42-inch mowers have a twin engine and it will cost you at least $100 more and they call it an upgrade! It's not an upgrade. We were mowing grass of 42 inch lawn mowers in the 80s with only 14 horsepower. You don't need 20 or 24 hp to cut your grass on a 42 inch mower. A twin-engine will almost always give you more problems than a single engine and its lifetime.
The twins also have more catastrophic failures where
there's very little that actually damages the singles to the point where they can't fairly easily and cheaply be fixed.
I do this every day as one of my businesses. I have laid hands on probably 12 to 15 lawn mowers today.
I don't like the riders so I don't really mess with them too much but I did quite a bit in the past several years.
Lawn mower engines are still little low perform little turds! Those 22 and 24 horsepower V-twin Briggs are right around 749 ccs.
24 horsepower for a lawn mower sounds like a lot but look at the CC's. It's pathetic. A Kawasaki Ninja in the late 80s had under 600 cc's I was putting out 75 to 100 horsepower.