Small Engines (Lawn Mowers, etc.): riding mower pops and stalls, air filter oil, valve clearances

Question
QUESTION: I have a craftsman dlt3000 model#917.273811 18.5 hp riding lawn mower! It will start and idles great, like brand new, but when I let up on clutch it makes a pop noise out front end and stalls! I had just changed battery,new spark plug,starter,starter cilinyiod,fuel filter, oil filter, air filter, oil, gas, cleaned out carburetor,checked valves,every thing seems normal.saftey switches? how many?

ANSWER: Is the transmission locked up?  What are your valve clearances?  Is the belt binding?   Does the engine run full speed if the clutch is pressed in?

Let me know.
Eric

---------- FOLLOW-UP ----------

QUESTION: the transmission is not locked up. I don't know valve clearances, and belt seems to be fine. I did notice that when I engage blades then disengage them the cable sticks open.

Answer
I would check the valve clearances as incorrect valve gap will cause popping.
Did you remove, dis-assemble and clean the carb with compressed air from an air compressor and carburetor cleaner?
Check the clearances and let me know what they are.
Eric