Small Engines (Lawn Mowers, etc.): B&S Engine in a MTD Yard Machine Mower, twin cylinder engines, briggs and stratton

Question
Have a 2006 MTD Yard Machine 38" Riding Mower with a 12.5 HP Briggs and Stratton Power Built Engine. When I try to crank it, it seizes up and makes a loud short humming noise. Originally thought a belt was bad. Replaced deck belt, and engine started. When attempting to engage deck blades, engine died. Tried to restart, wouldn't crank. Made humming noise again. Put it up on ramps and looked under. Had wife try to crank while I looked. It appears that the engine is not turning the deck belt, or the drive belt above it. Any ideas?

Answer
Hello Jason:

1- For the Starting Problem: Remove ALL the Belts from the Engine Pulley. Does the Engine Turn Smoothly when Starting, If No, then Reset the Valve Clearance. **I Do Not Use the Setting Called for by the OEMs. I have Found that the Following Works Best. Remove the Valve Cover (on the Dead Cylinder for Twin Cylinder Engines). Set the Cylinder you are Setting the Valves on to Top Dead Center (Both Rocker Arms will have Play in them when the Engine is at TDC) When Setting the Valve Clearance. Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .007in - .009in. I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. Be Sure the Piston is at TDC on the Compression Stroke.** 2- For the Engine Quits when Engaging the Blades:  **Check the Seat Safety Switch. PLEASE REMEMBER THAT THE INSTRUCTIONS FOR CHECKING THE SAFETY SWITCHES IS JUST THAT!!! FOR CHECKING ONLY. I NEVER Suggest a Mower be Operated with a Safety Device or Switch Disconnected or Bypassed. Now. On Some Model Mowers you can Simply Unplug the Safety Switch from the Harness. On Other Models you have to Place a Jumper Wire Between the Harness Terminals (on the 4 Post Switch Jumper from Same Color Wire to Same Color Wire). The Seat Safety is Showing No One is Seating in the Seat when the Clutch or Blades are Engaged.**  If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John