I have a Walker 2003 model GHS with 20 HP kohler. Less than 300 hours. It started gulping oil. About 3-4 ounces per hour. Motor had been babied and synthetic oil used except during break-in. The front cylinder spark plug was very oily. I replaced what seemed to be a bad head gasket on this cylinder. I tried the mower and the oil burning didn't slow down. I talked to Kohler and they said to take it in to the shop for diagnosis using a leakdown test and compression test. My mechanic called and said the vacuum was low (4) and he suspected a faulty reed valve. He replaced the part and said the vacuum came back up the normal range (10). The exhaust doesn't smell like oil any more. The repair was only $45. I was so happy. I hope this helps someone else with similar problem.