Expert: John C. Bridgers Sr. - 7/4/2007

Question
I have a Yardman 15.5HP OHV riding mower.  Engine info: Model: 28N777, Type: 0642-A1, Code: 961015ZD. The engine is made by Briggs & Stratton.
I was cutting the grass, everything working OK.  I throttled down to talk to someone.  I throttled back up, and the engine wouldn't go back up to speed.  It would barely keep running.  There was a lot more noise coming from the carburetor than usual.  It actually seemed like the timing had changed(firing too late).  I don't know what the real problem is.  The spark plug is fairly clean.  The oil is clean. Do you have any suggestions about where to start?  Thanks in advance for your help.

Answer
Hello Lee:

If you are Sure the Throttle Cable is Moving the Throttle Valve Shaft on the Carburetor, then Remove the Valve Cover and Check 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 When Setting the Valve Clearance. Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .003in -.005in and the Exhaust to .008in - .010in. I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model Numbers. Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. 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 you Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John