Small Engines (Lawn Mowers, etc.): 3 1/2 hs B/S lawn mower engine, briggs stratton, internal passages

Question
Hi, I have a 3 1/2 hp Briggs/Stratton MTD 20" push mower.  My wife put gas meant for the weed eater (two stroke) into the mower and cut grass for awhile.  The engine runs but the choke keeps coming on and then off repeatedley.  I emptied gas tank and replaced with fresh gas. Removed,cleaned and put spark plug back but the engine won't run solid, keeps cutting out.  What else should I do/replace/clean?  Thanks you for any help you can provide.

Answer
The problem is not associated with the two-stroke fuel but rather debris has entered the carb (from that gas can perhaps).  You will need to remove and clean the carb thoroughly including pushing a piece of tag wire through all of the internal passages and follow up with carb cleaner.  Hope this helps.