Small Engines (Lawn Mowers, etc.): Too Much Oil, engine model type, leak down tester

Question
I recently added oil (too much I think) to a perfectly running Bolens mower with a B&S engine.  Immediately after doing so there was an abundance of white smoke.  After draining some of the excess oil, it worked fine.  Now 2 weeks later, the plug is fouled.  The engine runs but there's no power.  I changed the plug but still no power.  What do you suggest

Answer
How long did you run the engine with too much oil?  What is the engine model, type and code number?  Is the engine on a push/walk behind mower or a rider?

You can cause internal engine damage by having too much oil.  Do you have a leak down tester to check the internal engine condition?
Send me the engine numbers so I can look up your engine.
Eric