Sure alot of the Kohler 20hp engines out there. We see a ton of them on commercial lawn care equipment and have had no major failures. One thing that Kohler seems to have alot of problems with is the ignition system. They use "Smart spark" and can be heck to diagnose. Also Kohler makes a cheap version: it cannot br bored oversize. Otherwise I have seen them see 3-5000 hrs before any major problems. I prefer the Vanguard twins over any other just because they are almost indestructible. When it comes to a single cylinder its Honda or Kawasaki, and Deutz diesels.
Just my simple minded opinion!
Daren Marshall
Hi-Pressure Solutions