Kawi 25hp running on 1 cylinder

Discussion in 'Mechanic and Repair' started by amarino, Jul 19, 2007.

  1. amarino

    amarino LawnSite Member
    from MA
    Posts: 25

    Pulled each plug wire, and it dies with one, no change with other. Getting spark to the bad cylinder. Pulled valve cover, everything mooving as it should. Checked valve clearances - they were a bit big, so changed them but did not fix. Pulled plug on bad cylinder, and its dry...shouldn't it be wet after running? Took carb off and dissasembled and cleaned. At the end of my rope :(
    Oh yea, started doing this 2 weeks ago, then ran OK since. I put a bottle of marvel mystery oil in fuel and its been fine until today.

    Any ideas?
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    When you cleaned the carb. did you also clean/flush the fuel tank and fuel lines then replace the fuel filter ?
  3. amarino

    amarino LawnSite Member
    from MA
    Posts: 25

    No, I just removed / dissasembled / cleaned carb.

    Update...even though I had spark at the bad cylinder I decided to swap coils. After doing that it ran better but still died when engaging blades. Took off each plug cap and it ran worse with each one so that tells me both cylinders are working. Adjused all valves to .006" and now runs good...not great...still seems to have less power than it used to. Could the valve adjustment be that critical? They WERE at .018, now at .006 (hot). Maybe they should be somewhere in the middle at .012? It is backfiring through the carb under heavy load.

    Its a FH721V 25hp Thanks for the response :)
  4. JHugh

    JHugh LawnSite Member
    Posts: 84

    The correct valve adjustment should be .004"-.006" when the engine is cold. What gap did you set your coils at? They should be .008"-.016". Just split the difference and call it .012".
  5. amarino

    amarino LawnSite Member
    from MA
    Posts: 25

    Coil gap??? Uhh, I moved them all the way back (farthest from stator) and tightened them there. Didn't know they had a gap also. Looks like I'm taking it apart again...

    I wonder if the lack of power/backfiring through carb is from the coil gap being too big?
  6. JHugh

    JHugh LawnSite Member
    Posts: 84

    To set your coil gap center the magnet on the flywheel with the ignition coil. Then set your gap. It may well be causing the backfiring. I throws the timing off when they are not set properly. Your spark is also weaker when the gap is set to wide.
  7. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    use a business card to gap your coils
  8. renegade929

    renegade929 LawnSite Member
    Posts: 8

    yup, that's what i did..works fine,actually used 2 pieces ripped from an oil filter box...just enough so the coil was not TOO close to the flywheel when spinning
  9. themowerman

    themowerman LawnSite Senior Member
    from NJ
    Posts: 297

    You might have a bad head gasket on the bad side. Take a compression test. Also make sure that your valves are moving the same distance when they open and close. You might have a bad cam issue. I have found that it is usually the exhaust valve.....
  10. Breezmeister

    Breezmeister LawnSite Bronze Member
    Male, from South Jersey
    Posts: 1,546

    Along with all that good advise, you might want to pull the head and check to see if the valves are seating correctly or if the valve seat has come loose.

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