My riding mower started smoking alarmingly yesterday, and I've never seen anything quite like this. It's a 10-hp B&S single, and whenever I hit grass thick enough to cause it bog down substantially, it blew an absolutely enormous cloud of acrid gray smoke. It was a pretty calm day and the second time this happened I was near the road in front of the house. The cloud of smoke remained pretty intact and casually wandered out onto the road. It was so thick, cars were slowing as they approached it. The first time this happened I shut it down immediately, and each time after that I pushed in the clutch until the engine recovered to normal, so I never let it continue to see whether it was actually going to shut down. And the first time it happened I did check the oil level, and it was full (I had topped it off before starting that mowing session). I had something similar happen with the same mower a couple of years ago, except it was far less smoke, but that turned out to be the carburetor having shaken loose a bit creating a leak at the manifold, so the second thing I checked after the first occurrence (after checking the oil level) was the tightness of the carb. But it was on tight. It was a pretty warm day, ~90º, but it's been about that temp most every time I've mowed for the past two months. Start-up seemed normal but this mower does burn 3-4 ounces of oil each hour of run-time. I do note that I can never seem to get the oil dip stick out with the level clearly indicated so I rely on whether there's oil in the 'Low' and 'Full' holes, and I do tend to err on the side of caution, so it might have been a bit over-full. Is this something that could be the result of too much oil? And of course my chief concern is that this might be an indication of looming serious break-down, worn or broken rings or some such. Ideas?

MTD Ranch King 1997 14AQ825H206 18HP Twin Briggs & Stratton Engine 42A707 This mower was bought from my uncle, who is disabled and hasn't been able to work on it for a couple of years. His brother-in-law supposedly did "work" on it. And by "work," I assume he stood there and looked at it, and scratched his privates. *sigh* [B]Problem #1[/B]: Will not start by using key. Will start when jumped at solenoid. Ignition switch replaced. Fuse between ignition switch and solenoid replaced. Key does have to be turned to on for it to be jumped by solenoid. [B]Problem #2[/B]: Will only run with choke fully out. Sputters and dies when choke it pushed in. Replaced choke cable. Cleaned carb. Is a replacement carb in my future? [B]Problem #3[/B]: Dies when put in high. Dies when blades are engaged. Pulleys, blades, and belts move freely. Had deck off and cleaned it. Deck is a pita to take off and put on. New belts. [I]Known issues[/I]: Aunt left it out in the weather for a few months. It died on her and she couldn't push it back to the garage. Gas has been replaced. I would also like to point out that I'm not a mechanic. My Dad was the one who fixed this stuff, and with him gone, it's fallen to me. And, being the youngest (and a girl), I was never allowed in the garage. So I'm getting a crash course in this stuff. [I]Be gentle.[/I]