Small Engines (Lawn Mowers, etc.): Snowblower wont start, briggs stratton, engine vibration

Question
Hi, I have a 2006 Craftsman snow blower with a Briggs/Stratton 8.5 hp motor. It's been running fine all winter but yesterday it started up no problem on the first pull then each time I tried to put it in drive or blow snow it would stall. After several stalls and restarts now it won't start at all. So far I have replaced the plug,both old and new are getting a very good spark. There is gas in the carb and I pulled the carb to clean it, the float and all small parts were spotless. When I turn it over there is spark and gas but it is backfiring out the carb maybe 2 times in a minute while cranking it over. I think the spark is not timed properly with TDC but how would that happen. ANy ideas would be great especially since we're supposed to get 12" of snow tonight.
Thankyou from Vermont!!

Answer
Hello Cort:

From your Description it Sounds like the Flywheel Key is Damaged (this can Occur when the engine is Shut Off if the Flywheel Nut has Loosened from Engine Vibration) and Requires Replacing or if this is an OHV Engine, the Valve Clearance May Require Resetting (this is a Common Problem with OHV Engines). Send me the Model and Type or Spec Numbers Off the Engine, Please. With these I can Locate the Proper Manual and Better Assist you. The Model Numbers May be Stamped Into the Blower Housing (metal engine cover) Above the Spark Plug. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John