Small Engines (Lawn Mowers, etc.): engin i.d., briggs stratton, shaft size

Question
i am trying to find out some info on my lawn mower engine. it is a briggs&stratton. there is a plate over the muffler with the numbers 121602 0269 e(b?)1 000706 fb. family ybsxs.1901ve 274474.
  the engine is smoking very badly. the plug fouls. other than that it runs fine. i would like to find out all info on this engine( bore,stroke, shaft size,etc.) so i can buy a replacement engine.

Answer
Hello Bill:

I have a Couple of Site Addys for you. 1- http://www.briggsandstratton.com/display/router.asp?DocID=64103 This is the Briggs Home Page. 2- http://www.outdoordistributors.com/ (1-877-707-2787). I Use this Company When Purchasing All My Short Blocks and Complete Engines. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

Good Luck

Respectfully

John