In my Kohler 25's work great.
My "junk" Kohler 25's (2 of them) have logged about 3400 hours with no troubles.
Plugs: Bosch Platinmum
Gas: 93 Premium unleaded June, July, Aug, Sept,
87 Unleaded March, April, Oct, Nov.
Oil: Mobil 1 15W-50 synthetic changed each 300 hours.
Air Filter: Stock w/ 5w-30 oil on pre-cleaner, kept pristine-clean.
Oil Filter: Deutch or Wix. NEVER NEVER a FRIGGIN FRAM!!!