Small Engines (Lawn Mowers, etc.): MTD 5HP Snowblower will not start, mtd yard machine, google

Question
It is an MTD Yard Machine, 5hp, HSSK50-67404S.  Ran great last winter.  This winter will not start in any choke setting and varying throttle does not seem to matter.  I have primed it as many as ten times with no result.

I would like to try the easiest things first, naturally.  The plug was  fairly nasty looking so I changed it but I cannot find the proper gap setting for this model.  The other question is where the next step is to go...?  Filter?  Water in the gas?  Carb?  

Thank you in advance!  

Greg

Answer
First check for spark.  Make sure the controls and the plastic key are in the start position.

If spark is good, then most likely the carb.

Check out this link:

http://www.cpdonline.com/692509.pdf

Also, Google Tecumseh carburetor rebuild or maintenance and you will find several good site describing how to clean/rebuild the carburetor.
Eric