About a day after i just bought a brand new 60" Super Z with a 28 horse kohler EFI, i realized the oil cap was loose and that the mower was loosing oil. at this time the mower had about 3,4 hours on it. shame on me for trusting the dealer 100% for putting the thing together. anyways, i added some oil, checked the level and went on. a couple days later, the engine started throwing out black smoke and wanting to die. when i turned the blades off it would quit. i checked the oil and found it had a little to much. after letting the oil out, it ran great for a while and yesterday it started doing the same thing again. Checked the oil again as i had several times since and it was fine. then i let the air out of the gas lines, cleaned cooling fins and other maintenance. today i ran it and after about 4 hours of use, it started again. dont have time to take it to the dealer right now because they are 50 miles away. plus it runs fine for long enought to do what i need to. any suggestions?