Small Engines (Lawn Mowers, etc.): Tecumseh 5hp engine, throttle plate, fuel flow

Question
I'm having a bit of a problem with my snowblower.  It has a 5 HP Tecumseh HSSK50 (spec 67404S) with a series 10 carb (as best as I can tell).  It will run great until you engage the blades or drive.  And when it hits snow, it really bogs down.  The spark plug was black and sooty.  I cleaned it up a bit with a file, set the gap and reinstalled.  There is good fuel flow to the carb. This carb has fixed jets (I took the carb apart and cleaned it, but will probably do so again after you tell me what "tag wire" is).  I'm wondering about the governor... any idea how to check it to make sure it is working correctly?  It does move occasionally, but is it moving enough?  Also, assuming the governor has the throttle plate wide open under load, do I assume that the problem is a dirty or partially plugged passage inside the carb?  Thank you very much for your time.

Answer
Hi Dan,

I would replace the spark plug, which may be fouled and shorting out or just not firing well under compression.  Sometimes they just can't be be cleaned.  

Tag wire is fine wire used for attaching tags to items.  If nothing else solves the problem, re-clean the carb.  You are right, the governor will hold the carb linkage at full throttle when the engine is under a full load.

Another possible cause of power loss is a worn engine.  Check the compression.

Good Luck,
Michael