Small Engines (Lawn Mowers, etc.): Engine Backfires through exhaust, noma snowthrower, valve adjustment

Question
I recently purchased a used Noma snowthrower.It has a 12hp OHV Tecumseh engine.  I got the chance to use it yesterday and it was backfiring through the muffler. I am just wondering if it is a electrical problem with spark, bad gas? or what I might check.

Thanks

Answer
You may have an adjustment on the carb but I doubt it.  Different regional areas can have slightly different carburetors.

The engine is either running lean, not enough fuel or too much air, or it could be mechanical or electrical timing.

Electrical timing is easy to check...just check the flywheel key.  Flywheel keys rarely shear on snowblowers.

Mechanical timing can be a simple valve adjustment to a bad cam.  Not likely to have a bad cam but the valve may need adjustment.

Here's what I would do.  Check out the carburetor and see if it has any adjustments.  Next check the bolts holding the carb to the engine...make sure they are tight.

If it still backfires then I would check the flywheel key and clean the carburetor.

Does any of this make sense?
Let me know.
Eric