Small Engines (Lawn Mowers, etc.): 6yr old B&S 4HP Yard Mach. white smoke. slow,slower, stop, stroke fuel, spark gap

Question
Marc, Great service!

The above Subject line basically says it. I recently paid to have new gastank and up-to-snuff repair.
The old gas tank was loose, I could tighten it, but repair said should replace tank because dirt had gotten in. ($65.00) Now, tank tight, but white smoke in exhaust (never before), and engine slowly cuts off after few minutes. I do not know how to adjust choke, spring, etc. (specs gone with the wind) The spark gap looked a little wide, I adjusted, and helped some. Suggestions?

John, Charleston, SC  

Answer
If you just had it repaired, can you take it back to get it done right?  Nonetheless, the only reason for white smoke is from burning oil.  Make sure the oil level is correct first (too high will make the engine smoke).  Second, is there any possibility that mixed (2-stroke) fuel was put in your mower?  Let me know what you find.  Hope this helps.