Hey, Jimmy
How about unsubstantiated rumors

?
Kawasaki, like all Japanese engines are notorious builders of strong, reliable and dependable equipment. They did have some models, equipped with phenolic cam gears that wore out prematurely...but, I think they have since rid themselves of that problem.
Kohler, also a fine engine builder, have had their problems with a relatively newer engine model, the "Courage" line. Often said "It takes Courage to buy one". They seem inherently weak and reported to break rods and/or governors long before their warranty ends. The company does stand behind their warranty and, I understand, have replaced hundreds without question. The problem remains...what do you have once the same engine is under your hood??
A few years ago, I purchase a Husqvarna with a great hydro transmission. The rider, in excellent condition, was bought AS IS because it had a Kohler Courage engine that let go at 31 hours. After reading up on forums like this one, I took the risk and bought it anyway....plus, I had a spare single cylinder, 13 HP Kohler waiting in the winds. The machine has performed flawlessly since the transplant. My wife uses it to mow 3 acres about every ten days and it still has the original blades, belts etc...here is a link to the engine swap and blown Courage:
http://www.mylawnmowerforum.com/for...forum/679-first-time-buyer-buying-used-2.html
You may want to take this with a grain of salt because everything I've written is only what I've heard

.
Mark