QuestionQUESTION: John - What I have done - I have the 17.5 HP B&S OHV engine - Read your specs for valve adjustment - Did set the valves, but am nervous about establishing TDC - Have removed shroud and am wondering if there are any timing marks on fly wheel to ease TDC task - Did gauge max travel of piston on compression stroke - When engine fired a backfire through carb happened, but engine ran fine - I am assuming as the magnets pass by the coil the plug fires and TDC is close - Also without any type of manual, is the exhuast the top rocker arm - Thanks - Dennis
ANSWER: Hello Dennis:
>>The Magnets will Assist you in Locating TDC, but Only if you are on the Compression Stroke.
>>The Magnets Pass the Coil 2 Times During the Operation of the Piston. Once During the Power Stroke and Once During Exhaust Stroke. >>It is Easier to Remove the Valve Cover and Watch the Valves Move. When the Intake Valve Closes, then when the Magnets get Close to the Coil, Stop and Check the Piston to Ensure it is Near TDC. Now Finish Moving the Flywheel Until the Piston is at TDC.
>>The Magnets on the Flywheel will Actually be Slightly Past or Just Before the Coil when the Piston is at TDC on the Compression Stroke. >>I Usually Mark the Flywheels of Any Engine I have Set the Valve Clearances on, so it is Easier to Locate TDC if Required to do so in the Future.
>>It Sounds like the Valve Clearances are too Close on the Intake Valve or it May be there was Carbon on the Valve Seat and it May Not Backfire again.
>>Please, Do Not Hesitate, If you Hit a Snag, if I Missed Something 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: John, I was able to verify TDC by using my trusty old Weidenhoff compression gauge (barely moved needle) - When adjusting the valves I found the rocker arms very loose which entailed holding them square to the valve stem while gapping them - My question is - Is this looseness common or does it show excessive wear? - Thanks for your help - Dennis
AnswerHis Dennis:
>>For Some Reason that Not Any of the OEMs can Say, the OHV Engines have More Problems with the Valve Clearances Staying Proper than then the Old Style Valve System.
>>I have Spoken with Technicians from Most of the Engine OEMs and get the Same Answer. They Really Do Not Know Why the Engine Valves have to be Set about Every 3 to 5 Years.
>>If you can get the Proper Adjustment and Still have at Least 1 Complete Thread Left Showing on the Adjuster, then the Wear is Not Excessive. If there is Less than 1 Thread Showing on the Adjuster, then Use Thread Locker to Assure the Adjuster Lock Does Not come Loose During Engine Operation and Loosen the Valve Adjuster.
>>If More than 1 Thread is BELOW the TOP of the Adjuster Lock Nut, then there is Excessive Wear to the Adjuster, Rocker Arm or the Valve Tip. **If this is Suspected, then a Small Engine Service Center May be Required to Repair this Engine. There are Several Components in the Valve System that Need to be Checked for Wear at the Same Time as the Valve Stem, Rocker Arms and Adjusters.
>>Please, Do Not Hesitate, If you Hit a Snag, if I Missed Something 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. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
