Small Engines (Lawn Mowers, etc.): changing engines, briggs and stratton, hp briggs

Question
my brother had a 14.5 hp briggs and stratton engine that he put on a huskee body.the engine was running great on the old body.but, now it just cranks over and will not start.also,there is a yellow wire that he can't find where it goes.can you help?

Answer
Yellow wire from where?   IS it coming off the engine or the tractor wiring harness?

Is there a little solenoid coming off of the bottom of the carburetor?  If there is there needs to be a wire running to it that activates when you turn the key switch on.  This is called a fuel shutoff solonoid, when you disconnect the wire running to it it shuts the fuel off running to the carburator.

HTH