Tecumseh 13hp Engine **please Help

Discussion in 'Mechanic and Repair' started by sarah, Aug 29, 2007.

  1. sarah

    sarah LawnSite Member
    Posts: 24

    Hello~~
    I hope someone can help..This Murray riding mower is backfiring Really , really,loud..its a 13HP OHV130 engine(Tecumseh)..I cannot find TDC..some say its where the 2 magnets on flywheel line up with Coil housing..BUt MY TDC is 6 :dizzy: inches away from that(clockwise)..is it possible my that the flywheel key broke?? I adjusted valves..maybe one burnt..I smell something burning from exhaust..smells like burning brakes..
    I have :
    (1) backfiring..got better after valves adjusted, but do not know if I had correct TDC
    (2) loss of power
    (3) engine surges,then cuts out
    (4) replaced fuel filter, air filter, spark plug, cleaned fuel tank out..still running like crap..all black dry soot in exhaust hole and old plug was covered with black, dry soot..
    ANY IDEAS/ Suggestions: PLEASE HELP..burnt valve, flywheel, seat switch?????:dizzy:
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    First, Welcome to LawnSite.....


    Since your not sure you were at TDC compression stroke when you adjusted the valves this is where you need to start;

    With the plug wire off grab the flywheel and rotate it clockwise until you feel it get harder, This is the beginning of compression stroke. Stop turning at this point and remove the spark plug and insert a small screw driver into the plug hole.

    Slowly continue to rotate the flywheel clockwise until you feel the piston touch the screw driver and start pushing it out of the plug hole. From this point move the flywheel back and forth while holding the screw driver against the piston until the screw driver is sticking out the most.

    This will be TDC compression stroke and the position to check/adjust valves so re-check your adjustments, If you find the valves off correct them then try test running the engine again.

    If the flywheel key was sheared and the flywheel was 6" off it wouldn't run at all, Since Tecumseh does use off-set keys on some engines the only real way to check one is remove the flywheel and LOOK at it.

    Sooty black plugs could be caused by sheared key/valves out of adjustment or rich running carb/choke not opening ALL the way.

    Maybe this little bit of info will help.....

    Good Luck
     
  3. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Posts: 923

  4. sarah

    sarah LawnSite Member
    Posts: 24

    Hi you replied to my riding tractor question.,.many thanks..its a 13hp Tecumseh engine, model40541x99C
    OHV130-206810D
    My MAIN question is IS DC on this engine suppose to be where the 2 magnets on FLYWHEEL line up with the coil???
    As I said, it appears my TDC is at 6 oclock verses at 3 oclock if looking at flywheel..it runs and STARTS after I adjusted the valves, but stalls out after about 30 sec to a minute..backfires a bit, not as bad after adjusting valves..don't know if I am on TDC
    (2) CAN this tractor still runs if I sheared the flywheel key and it being off that much?
    (3)I smell something burning coming out of exhaust manifold..it seems JUST like brakes burning..could my engine head gasket be cracked or broken???
    (4) Put in new plug, new air filter, new fuel filter, cleaned gas tank
    (plug still getting foaled with carbon..black, dry soot
    (5)Hope u can answer all above!!! THANKS
     
  5. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Posts: 923

    "don't know if I am on TDC"
    Rob told you how to check that-

    "(2) CAN this tractor still runs if I sheared the flywheel key and it being off that much?"
    That's 90 degrees off. Unlikely it would run.

    "(3)I smell something burning coming out of exhaust manifold..it seems JUST like brakes burning..could my engine head gasket be cracked or broken???
    (4) Put in new plug, new air filter, new fuel filter, cleaned gas tank
    (plug still getting foaled with carbon..black, dry soot"

    That tends to indicate the engine is running either-
    Very rich
    and/or
    Very poorly.

    Start by checking TDC and then valve adjustment as per Rob.
    Hint- You will have MAX valve clearance at TDC. Try rotating the engine in small increments just before AND after TDC and see if the valve clearance is MORE than what you set it at any position. It shouldn't be.

    You may have a carb that is running excessively rich, allowing unburned fuel vapors into the muffler and then "exploding".
    Poor/intermittent ignition could do the same. (bad coil?)
    A bad head gasket would more likely appear to be an oily, black deposit on the plug.
     
  6. sarah

    sarah LawnSite Member
    Posts: 24

    Hey Thanks for emailing me
    I am going nuts here with this thing..I mean on a car, I can see the marks for TDC..I only see ONE MARk on this Murray;) ..its on the Flywheel housing with a white line..not sure what it is suppose to line up with..some small mowr repair guys SWEAr that TDC is where the 2 magnets on flywheel line up with coil..
    All I know is I am not too good at finding TDC .I will try what you say to do..
    would a faulty safety switch cause it to backfire, too? Just wondering..I haven't checked that.
    The carb seems fine..I cleaned it all out..same problem..maybe it is a bad coil..any way to check COIL before I buy another??
    And do u think flywheel key could be broke..mower starts..runs uneven, then bacfires and stalls
    OKAY..wish you were here to fix this tractor, guys!!
     
  7. sarah

    sarah LawnSite Member
    Posts: 24

    Hey Thanks for emailing me
    I am going nuts here with this thing..I mean on a car, I can see the marks for TDC..I only see ONE MARk on this Murray;) ..its on the Flywheel housing with a white line..not sure what it is suppose to line up with..some small mower repair guys SWEAR that TDC is where the 2 magnets on flywheel line up with coil..
    All I know is I am not too good at finding TDC .I will try what you say to do..
    would a faulty safety switch cause it to backfire, too? Just wondering..I haven't checked that.
    The carb seems fine..I cleaned it all out..same problem..maybe it is a bad coil..any way to check COIL before I buy another??
    And do u think flywheel key could be broke..mower starts..runs uneven, then backfires and stalls
    OKAY..wish you were here to fix this tractor, guys!!
     
  8. johnp900

    johnp900 LawnSite Member
    Posts: 71

    You need to get back to the basics. Did you replace the O ring in the main jet of the bowl? There are two o rings to replace.
     
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Sorry, But in my 16yrs I have never payed this any attention when setting a engine at TDC to adjust valves. Simple reason being when only adjusting valves the flywheel cover does not have to be removed.

    Just for the record both intake and exhaust valves should be adjusted at .004" @ TDC.

    Below is out of the manual that Bill posted the link for;

    "Set the valve lash with the engine cold, the
    piston at T.D.C., and both valves closed. Insert
    the specified feeler gauge between the rocker
    arm and valve stem. Adjust until a slight sliding
    drag is felt."

    No details as to find TDC as I posted above, The procedure I posted will work on ANY 4 cycle gas engine including automotive (was in that biz also).




    The flywheel key very well could be PARTLY sheared throwing timing off which would cause the engine to run hotter than normal giving off what you smell. It could also be caused from a loosely adjusted exhaust valve not staying open long enough causing excessive heat build-up.

    If you take this repair in the suggested steps the problem could be solved.....


    Me Too, I most likely could have had it fixed in the time it took to type this post....:)
     
  10. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Below is the two 'O' rings that johnp900 mentioned, Either one being bad could cause a rich run situation. But I feel you need to make sure the valves are adjusted correctly first to eliminate that as a problem.


    [​IMG]
     

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