Scag w/25hp kohler..cuts out after..

Discussion in 'Mechanic and Repair' started by mowisme, Dec 1, 2007.

  1. mowisme

    mowisme LawnSite Senior Member
    Posts: 899

    Hi- I have a scag STHM with a 25 hp kohler on it and a scag snowblower. works awsome..for 3-5 minutes, then seems to start to cut out..or run on one cylinder? runs fairly smooth but only after I take the load off. I thought I cured this problem earlier in summer when I re-set valve gaps and put two new coils on. but problem returns after running a bit? also back-fired once and shot flame out when I shut it off? any ideas would be great help. Merry Christmas all- Gene p.s. not super good starting either..but not bad.
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Are you sure this is a 25hp Kohler you adjusted the valves on ?

    If so, How did you do this ?
     
  3. mowisme

    mowisme LawnSite Senior Member
    Posts: 899

    hi - yes I'm sure it is a 25 Kohler command. ( was replacement..not original - think suppose to be 23hp?). I adjusted by bringing piston to TDC (power stroke) and used feeler gauge. can't recall, but think was set at .06 or .07 but don't really recall now. Gene
     
  4. mowisme

    mowisme LawnSite Senior Member
    Posts: 899

    Does this sound like a valve adjust problem? maybe I should re-adjust? anyone got the spec's for this on a 25hp kohler? and maybe a run down on procedure if not to much hassle- thanks much Gene
     
  5. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Post me the model AND spec numbers off this engine and I'll be happy to post the procedure.
     
  6. mowisme

    mowisme LawnSite Senior Member
    Posts: 899

    thanks Rob- here goes: Model CV25S
    Spec 551310
    Disp. 725cc
    S.N. 2626212817
     
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023


    I must be spending waaay too much time in my hole in the woods !

    I'm not sure what you have there, That spec number is not shown on my dealer's site, All specs start with 695 and only have five digits.

    I have never seen a CV25 with adjustable rocker arms (valves), They have hydraulic lifters and are self adjusting ?

    If the serial number is correct it states this engine as built in 1996, Seems if it did have adjustable valves it would be listed in the manual since it was issued 3/94 ?

    Below is what my CV17 through CV750 service manual shows, Torque to 100 in.lbs.


    [​IMG]



    Start the engine and run it till it starts acting up, Check for spark on each cylinder. You could have a coil breaking down after warmed up.
     
  8. mowisme

    mowisme LawnSite Senior Member
    Posts: 899

    thanks Rob- there was a 'specialty' tag or something simular next to the factory label. It came off thou. I will do the ignition test when warm..Those coils don't even have 1/2 hour use yet thou. just repklaced this summer then used machine today.
     
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Believe it or not I have pulled out of the box brand new coils and spark plugs to find them bad. Besides, This test only takes a minute and will tell you if it is ignition/fuel or a mechanical failure. Gotta start somewhere.......
     
  10. mowisme

    mowisme LawnSite Senior Member
    Posts: 899

    your absolutely right Rob..and this test is a easy one- thanks for all your help. I'm leaning on thinking a head gasket might be the culprit..96 engine would be a likely canidate by what I've heard the older ones didn't seal as well? but..one test at a time. Gene
     

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