Troy Bilt self-propelled mower won't start
This is a bit detailed, but I want to get all the info out up front:
Troy-Bilt Smart Speed Self-Starter Mulching Mower Model 569
has a B&S Intek engine
I purchased the mower new from Lowe's in 2004. I ran the mower for 3 years with no problems...and no maintenance. No oil change, no filter change, no battery charge, no spark plug change. Nothing but adding gas. Mower still ran great. But at the end of last summer, the mower gave up the ghost. It had been running rough for a few weeks, and then it finally stopped running completely. I changed the spark plug out and it started and ran for another 10-15 minutes and then quit again. Nothing seemed to get it running again. When it stopped running, it wasn't like there was catastrophic mechanical failure. It's almost like it was out of gas (it wasn't). I borrowed a neighbor's mower to finish out the season.
I started out this season by checking the oil (dipstick was bone dry). So I added a fresh 20 oz of synthetic oil. I also changed out the air filter (which was basically just a grass mat by now). I filled the tank with left-over gas from the previous season (probably a bad idea), primed per the owner's manual, and tried to crank it up. Nothing. I would give the pull-cord a couple of tugs to set the engine, then engage the electric start. The only reaction I would get is a little cough as the engine turned over. I talked to my dad, who recommended tugging the pull-cord ~20 times and then try to start it. I did that, and the enine actually came alive! It started up, belched a cloud of white smoke, foloowed a second later by a cloud of black smoke, and then it died. Nothing I did from that point forward has been able to get the mower started again. I back to just lifeless coughing when I set the engine up with the pull-cord and try the electric start.
Given how many systems I've prepped, I'm thinking this is either a very simple fix or a major problem. Any help would be appreciated. Also, if I'm leaving something out and any more info is needed, I can answer or find the answer. Thanks in advance.