QuestionI have a sears lawn tractor with the above described engine
Model 445677, type 0476Ei family 6Bsxs 7242vf 276480
It developed a loss of power, found it wasn't firing on one clylinder, removed valve cover. Both push tubes bent and displaced. No indication of valve piston contact nor bent valves. Checked other cylinder and it was OK.
I have no idea what caused this since I am unfamiliar with the internals of this engine. Do you have any ideas? schematics.\
I pulled the engine
AnswerHello Bob:
>>The Probelm with the Push Tubes is a Common One since the OHV Engine has become a Popular Engine with All the OEM's.
>>I have Inquired to Most of the OEM's for a Reason for the Valve Clearances Opening Up and Requiring the Valve Clearances to be Reset Every 50 to 100 Hours of Operation or Even Bending the Push Tubes as in your Case.
>>None of the OEM's had an Answer for me Other than 1 who Told me they were Looking into the Problem.
>>That was 8 or 9 Years ago and the Problem Still Exists.
>>Usually the cause for Push Tubes getting Bent is the Valve Clearances become too Wide and the Slap of the Tube Against the Rocker Arm causes the Tubes to Bend or in Some Rare Cases the Valve Stem Sticking in the Cylinder Head.
>>This is a 445677-0476-E1 Engine.
>>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 (5 or 6 Digits) and Type Numbers. Example: 445677-0476-E1. Then Double Click on the Model in the Results Area. Select Sectional Index. Now you can Select the Section of the Engine you Wish to View. Select the Cylinder Head, Gasket Set-Valve, Valves File to View the Push Tubes and Valves.
>>There are Usually Different Material that the Intake and Exhaust Valve Push Tubes are Made from.
>>The Intake Push Tube is Usually an Aluminum Alloy and the Exhaust Push Tube is made from Steel.
>>The Following is a Basic File I made for Setting the Valve Clearances. Any Input is Appreciated.
>>**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).
>>Check the Push Tubes and make Sure they are Not Bent.
>>Set the Cylinder you are Setting the Valves on to Top Dead Center on the Compression Stroke When Setting the Valve Clearance. Now Loosen the Valve Adjuster Lock and Using a Blade Style Feeler Gauge, Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .004in - .006in. Loosen and Tighten the Rocker Arm and the Feeler Gauge is Placed Between the Rocker Arm and the Valve Top where the Rocker Arm Pushes on the Valve.
>>***BE SURE TO TIGHTEN THE ADJUSTER LOCK AFTER YOU HAVE THE PROPER VALVE CLEARANCE***
>>If you Remove the Valve Cover and then Turn the Engine by Hand, you can Watch the Intake Valve Movement. When the Intake Valve Closes, the Piston will Just Starting the Compression/Power Stroke.
>>Position the Piston so it is Completely at the Top of the Cylinder and then Set the Valve Clearances.
>>Be Careful and Don't Jam the Wire in the Cylinder. Usually the Piston will Push the Wire Out of the Spark Plug Hole with No Problems.
>>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. Have a Happy Holiday Season and May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 3 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. Follow Up Questions are Now Accepted Anytime. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
