Small Engines (Lawn Mowers, etc.): mower is over reving, inch lbs, throttle lever

Question
I have a craftsman 42" mower with a 15.5 Briggs motor. the motor started revving at full speed. the throttle lever and linkages look intact but will not lower the motor to idle. it is all or nothing. Mower model number is 917.272350

Answer
It sounds like your plastic gov gear inside the engine is broken.  You will need to remove the engine from the tractor, remove the bottom cover and replace the plastic gov gear.

Be sure to use a removable  loctite and new gasket when reinstalling the sump cover to the bottom of the engine. You should torque the bolts in a staggered sequence to 210 inch lbs.  (16.0 Nm)

Happy tinkering