QuestionQUESTION: Have a Tecumseh 17 hp OHV engine in my riding mower that won't start. The engine will turn over almost 1 revolution each time I try but seems to have too much compression. Engine model is OHV17 20461B (H). Engine Family STP490U12RA, Displacement is 490. Have a new, completely charged battery in the mower but still does not seem to have enough power to continually turn the engine over. I am thinking the valves may need adjusting, which I have sucessfully done in the past on a Briggs engine but not a Tecumseh. Can you provide any suggestions to get this engine running and provide the min/max valve setting for each valve (intake and exhaust).
ANSWER: Hello Keith:
This has Become a Common Problem with the OHV Engines. You need to Reset the Valve Clearance. The Compression Release is Not Operating Properly and Resetting the Valve Clearance will Correct this Problem. **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) on the Compression Stroke When Setting the Valve Clearance. Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .004in - .006in. 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.** 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
---------- FOLLOW-UP ----------
QUESTION: Thanks for the info. How do I ensure that I am at the compression stroke? With the B & S engines I have messed with in the past I removed the spark plug, rotated the flywheel by hand until I felt the engine expel air then stuck a screw driver in the spark plug hole to ensure the piston was at its closest position to the cylinder head. Will this method work the same way with the Tecumseh?????
AnswerHello Again Keith:
The Best Way to Ensure the OHV Engine is on the Compression Stroke (even Briggs) is to Watch the Intake Valve Operate and when it Closes; Bring the Piston to TDC by Inserting a Pencil Into the Spark Plug Hole Until it Touches the Piston. When it Stops Moving, the Cylinder is at TDC. 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
