Small Engines (Lawn Mowers, etc.): Back fires from exhaust, type numbers, charging system

Question
John Deere riding lawn mower.  Engine model 191707 type 5640 01 code 781 22112.  8 HP

I stopped the engine by grounding the spark plug to the frame.  Ever since I did that it won't run and back fires some time when I try to start it.  did I damage the stator (electronic ignition) or the magneto?

Answer
 Hello Kevin:

 This Engine has Points Not Electronic Ignition. The Stator is the Charging System for this Engine. Go to this Addy http://shop.briggsandstratton.com/BShopProductListingPage.asp?rsvp=0&PARENTID=0&... and Enter the Model Numbers 191707 and the Type Numbers 5640. and Click Search. Then Select View PDF. This will Download the Breakdown/IPL for you Engine. On page 2 of 12; Diagram Box # 375 Containing #'s 340, 342 and 516 are the Point Set which is Located Under the Flywheel. The Points Set Contacts are Sticking. Shutting Off the Engine the Way you did shouldn't have had Any Damaging Effects on the Engine or the Points Set, Unless the Point Set was Old and was Burnt to Begin With. Replace the Point Set. The Gap for the Contacts is .020in and the Flywheel and Coil are Gapped to .020in also. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John