Small Engines (Lawn Mowers, etc.): Go Karts, combustion cycle, auto mechanic

Question
I have a Yerf Dog Go Kart with a 6.5hp Tecumseh.  The engine model # OH 195 EP.  It's fairly new apx. 25hrs. of use since we opened the box.  The problem is while driving the engine gets stuck in the accelerated position, that is to say when i release the gas pedal it should coast down to an idle but instead it shakes and stumbles hoping to keep going at this point I can do one of two things I can keep driving untill it passes or let it die. Which leaves it stuck and hard to push because you can feel it going through the combustion cycle. I was an auto mechanic. And would take it to a repair shop but transporting it and the fact that during the pushing eventualy it does return to normal but this problem prohibits me and my kids from leaving the property to  explore.  Any advice?

Answer
Are there any adjustments on the carb other than the idle?
Will the engine idle normally?
Are the carb and tank mounting screws tight?
A long shot, but we frequently find bad spark plugs.

Have to spoke with a Tecumseh engine dealer.  If the engine is that new there may be a warranty repair.

Let me know about questions.
Eric