George, you are right. Kohlers are prone to certain RPM vibrations, especially low idle. I had one K321 (probably my favorite Kohler, such a powerful guy with great versatility) that I had adjusted to the point to where it would sit there and literally rock back and forth on the floor as it staggered along at idle. That one was untouched with factory installed balance gears too.
I just know from rebuilding countless Kohlers that the only balance gears that blow up are those that are installed incorrectly (easy to do... ask me how I know sometime when its not embarrassing ) end up with bad bearings, or are used at high non-governed RPM. Cast iron can't take that much centrifugal force without blowing to smithereens.
Kohler installed them for a reason. I forget where I read the scientific breakdown of how they work, but from my experience and from those who I have talked to in the performance world, they actually do more than balance the vibration. My belief from doing some history research is that they are designed to increase power by reducing friction and the physics of having to overcome the "throwing" force of a piston and rod. I know Kohler claimed that they also affected fuel economy, not like that really matters to us.
However, the opposing side will say that if the ol' balance gears are so great, why didn't every other small engine manufacturer join in? I simply don't know. I know Kohler guys have struggled installing them from day one, and I know early balance gear failure gave them the reputation as the Achilles heel of the K series.
Personally, I like them. When I do a rebuild, they get rebuild and they go in, timed right.
Here's something else to chew on. This is the most scientific thing I know to throw in this discussion.
Kohler engines with balance gears have smaller crankshaft counter throws. A counter throw is every other manufacturer's way of balancing compression and the explosions of combustion. When you take out the balance gears, you have an engine out of balance even more than what you have on any other engine. That is rough on the main bearings, hard on the cylinder, and will wear out the engine faster. What I am saying is that a Kohler crankshaft is not setup the same as (say) a Briggs. Balancing via two gears instead of a real counter throw was a Kohler innovation, maybe wrong but innovative nonetheless. Once I learned that, I started doggedly believing that the Kohlers need those two little doohickeys to last well.