Small Engines (Lawn Mowers, etc.): Murray Riding Mower, engine model type, carburetor

Question
I recently was given a Murray 12.5 hp riding mower, probably 4yrs old and i've ran it twice and it ran fine as long as i kept the throttle at 1/2 to 3/4 open..  when i would run it full throttle it would run fine for a minute then shut down completely... so i ran it about 1/2 way open those 2 times...   this last time i mowed it was getn late and of course i ran it around 3/4  open.   Well it ran fine for about a minute and then slowly went dead.  I got it running long enough to  make it back inside my fence and thats it.  it will turn over and run for a few seconds and kill off again.   i've check the plug, drained the gas and refilled with fresh gas, and checked the bulb. Please help

Answer
What is the engine model, type and code number so I can look up your carburetor.

Most likely you have a dirty carburetor.  If you remove the air filter and spray starting fluid in the carb can you keep the engine running while spraying the starting fluid into the carb?

Let me know.
Eric