Small Engines (Lawn Mowers, etc.): snowblower engine, reed valves, blowing snow

Question
I just got a used snowblower craftsman 7/26 tecumseh 7hp I got it running but when blowing snow it slows down until it stalls or until I stop engaging I noticed that it also sparks all around the muffler when snow is flying around This is an older model not sure of year guess about mid 80's

Answer
David
Clean and rebuild the carb...
Another thing could be a failing coil. Sometimes they fail as they get hot. Since it's cold out, maybe it's reaching a point of "limbo" where it's almost hot enough to quit, but not quite. You might compare the spark output, cold vs hot.
If it is possibly an older unit, they had reed valves that would break and cause this problem also. They are under a small rectangularish cover w/ 2 screws on the block near the blower housing top right of carb area.