Walk Behind Lawn Mowers

I have a 6021P mower with a Kohler 149 CC engine. S#022312M002140 Purchased in March 2012. Since it was first used the engine will sputter occasionally and belch lots of heavy blue smoke. This may happen once or twice per month and not at all with other times. My local dealer is 3 weeks behind on even looking at the issue and I know that when I take it in it will be one of those times that we cannot make it duplicate the problem and the dealer will tell me nothing is wrong. Clearly this is not normal and may be a signal of impending engine failure. What am I to do? Oil levels are in the normal range and all maintenance has been as directed in the manual.