Small Engines (Lawn Mowers, etc.): tries to die in low idle.., valve model, engine tune

Question
I have a craftsman 20.5hp engine. When I put in low idle in tries to keep dying.. It runs then it seems it will shut off then it runs again. sometimes backfires when I shut it off. has been running fine until this year. I do empty the gas and change everything your suppose to every year. Should I remove the carb and clean? or is there something else I should check? Also it runs good when blades engaged (load)..

Answer
How old is the engine?  It sounds like the low speed carburetor circuit it causing the problem.

Are there any adjustments on the carb other than idle speed?

Most likely you will have to clean the carb but I would check the following: air filter, fuel filter, spark plugs.

When was the last major engine tune-up?  Is your engine an over-head valve model?
Let me know.
Eric