QuestionQUESTION: I have a Sears mower with Tecumseh 6.75 hp motor (143.006700 YTPXS.1951BA). It became harder to start and I found both flywheel and blade keys were sheared. I replaced them but the pull rope was still hard to pull. It will start (and run fine) if I can pull the rope hard enough but it will kick back most of the time. I have taken the motor completely apart and everything looks good. If I leave the plug wire off it still pulls hard (pulls easy with plug out). I believe the compression release that I see on the cam assembly is not opening the value for start up due to a loose valve setting. I looked in the value box by the intake but I see no way to adjust the valves. Can they be adjusted (I believe that is my problem) and if so how and what are the clearances? I have done a lot of engine repair with no problems so this one is really getting to me. Thanks for the help.
ANSWER: Hello Bruce:
The Valve Clearance is Set by Removing the Cylinder Head and Removing the Valves. Lightly Grind the Valve Stem Tip and Slide the Valve Back Into the Engine. Hold the Valve in Place and Check the Clearance Between the Stem and Tappet. Be Sure the Engine is on TDC of the Compression Stroke. The Valve Clearance is; Intake Valve Clearance to .004in -.006in and the Exhaust to .007in - .009in. From your Description, I Believe you are Correct About the Compression Release Not Functioning Properly. Reset the Valve Clearance. You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.outdoordistributors.com/ and Select the T. Then Select Tecumseh. Then Select Don't have Part Numbers. Then Enter the Model Numbers (143.006700). Then Select your Model and Download the File for Online Viewing. 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: I checked the valve clearances and both are in the proper range so no adjustment is needed. When I took the motor apart before I saw the lever on the cam assembly that helps hold open the exhaust valve for decompression on start up. It looked like maybe a 1/16" to 1/8" lift for the devise. Is that about right or is it possible the lever has somehow worn down to not open the valve enough? This mower is not that old and the rest of it looks almost new. The lever moves freely and the spring holds it in the forward position as it should but even on a slow pull through of the motor it doesn't seem to be working as there is still a lot of compression. Have you ever heard of that part of the cam assembly going bad. The pad the cam riser rests against does not look worn in the area the riser touches it. Bless you for your help.
Bruce
AnswerHello Again Bruce:
WOW, you do have a Problem. OK. From your Description the Lift for the Compression Release Sounds Good. You Do have a Blade Mounted on this Engine, Correct? If No, then that can Cause the Problem. The Blade is a Counter Weight and is Required for Most Engine of Less than 8 to 10hp. I have Replaced Very Few of the Compression Release Assemblies. They Do go Bad, but it is Rare. Is the Oil Pump Moving Freely? If the Oil Pump is Binding it will Cause this Problem. Is the Coil Properly Gapped (.020in). It May be Striking the Flywheel and Cause this Problem. I will ask my Dad About this One. I have Covered All the Usuall Causes and like you, I am Stumped if the Above Items Do Not Correct the Problem. 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
