Outdoor Power Equipment and Small Engines - Murry Enduro 16.5 Tecumseh Riding lawnmower help

I have a Murry riding lawnmower that idles irrattically and back fires while running. It does not matter if the engine is warm or cold. I changed the spark plug and filter but still no improvement. The mower does not start hard, but blows a heck of a lot of smoke when first started. It idles high for a second then idles low then will back fire. It will do it when I am driving it. Can some please give me an idea where to start?

Murry Enduro Tecumseh 16.5 engine--Model:ohv165 204407c (H)
The year is unknown.

I would say it's a carb problem. If it has the plastic bowl carb on it, I suggest cleaning out the carb and installing a bowl kit. Does the oil smell like gas?

Step 2 if needed, might be to look at the valves to be sure they are moving freely and seating properly.