Well, it isn't unreasonably loud. Guess it is just the difference between the two engine designs. The engine sound is harsher but I will get used to.
By the way, I bought this mower used, supposedly 3 months old and looked like it just came out of the crate. I was surprised it had the Kohler engine, but it is original since it matches Kohler decal on side of mower.
Also interesting, the deck seemed to make a lot of noise. I found one of the idler pulleys was loose and sitting at enough of an angle the lower edge was rubbing the top of the deck. From paint on the nut it appears it had never been tightened down.
Then decided to change blades and found one of the original blades was not flat, but had about a one-half inch bow in it. No wonder it seemed to cut shorter on one side than the other no matter how much I adjusted the leveling. It's cutting better with the new blades.
John