I have this problem since I bought my mower (Kohler 27 HP). After about 3 hours on the mower the next day I start it up and blows white smoke. I thought maybe it has to break in. Well when I got 7 hours on it I changed the oil, filter, etc. Every so often I will start it and it blows smoke and fills my garage. Then goes away after a min or so. If I run it high it burns of quicker but I let it idle. I think it was the stupid dealer. It sat for a year and in front of my starts it up after jumping it and runs it full speed!!!!!!!!!!!!!!!! I mean for 5 min straight! My freakin Kawa motor from 03 that has 15HP and has over 3,000 hours never smokes!! I was never a fan of Kohler. It only happens when the motor is cold or if the trailer jumps a lot. The oil is on the full mark. I really want to put Mobil one but use castrol 10-30. I read something about the 25HP with the needle float or the valves.