weak spark on Kawasaki 18hp

Discussion in 'Mechanic and Repair' started by MowerMinister, Mar 20, 2013.

  1. MowerMinister

    MowerMinister LawnSite Member
    Posts: 9

    I've got a Kawasaki FS541V AS07 R. A few weeks ago, the engine was constantly surging at high RPMs. I discovered that the muffler was cracked on both sides so after a small welding job we were back in action. Now its surging at low RPMs and a closer look revealed that I'm only running on one cylinder. I checked for spark on the the weak cylinder and had no spark. I removed the coil and cleaned the rust off of it and the magneto as well. I replaced it and put it back to the factory gap specs with a feeler guage. I have spark now but its very weak. I've rechecked the gap and everything. Does this mean that I have a bad coil? The other cylinder has great spark and the engine runs fine on that one cylinder its just weak when the blades are engaged. I'm assuming I have a bad coil but in the interest of saving my company money I wanted to make sure that there isn't anything else I should check before I start buying parts to resolve the issue.
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Swap coils side to side, If the other cylinder stops running buy a new coil.....
     
  3. MowerMinister

    MowerMinister LawnSite Member
    Posts: 9

    swapping coils only cured part of the issue. I'm still running on one cylinder even with a new coil installed because the old one ohmed out. Could it be a carburetor issue or maybe a valve problem on that cylinder?
     
  4. Valk

    Valk LawnSite Silver Member
    Posts: 2,711

    New spark plug with proper gap? Just sayin'...
     
  5. Landrus2

    Landrus2 LawnSite Platinum Member
    Posts: 4,811

    unplug the white wire from the coil (this wire kills your spark via ignition swith or safety switch:waving:
     
  6. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Wouldn't an intermittent ground kill both the coils at the same time..??
    Man...that avatar looks familiar..????
     
  7. Landrus2

    Landrus2 LawnSite Platinum Member
    Posts: 4,811

    Sorry I have orders to ignore you so no comment:waving:
     
  8. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Not likely the carb being a single barrel feeding both cylinders, Possible intake gasket leak. Check by spraying carb & choke cleaner around the intake while running, Other thing is valve issues. Check the valves/adjustment, Should be 0.0039~0.0059" at TDC compression stroke....




    Yeah Slapper...... Ole Joe didn't do a very good job at starting over with a new user name.....
     
  9. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,064

    Have you pulled the plugs? What did they look like? Are you checking spark with a spark checker ? Should be able to jump a 1/4" gap.

    With Kaw., the coils have an internal diode, so to accurately check them you have to pull the kill wire off both coils.

    Per KAWASAKI :" No spark, one side - V-Twin"

    " Isolate ignition coils. Connect gap style spark testers to the coils, grounding the testers to the engine. Unplug the shutoff wire from each coil. If the coil that had no spark still does not spark, replace it, this is the most common reason for no spark on one side. However, if spark returns to the coil that had no spark, the opposite coils internal diode has failed. The diode failure causes no spark at the opposite coil." ( when the harness is hooked up)
     
  10. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Good info Fish...
    Just wondering...if you installed a diode between the coils...like Briggs did on the old Vanguard twins...
    Would that work around the problem..?? Or does the diode failure weaken the coil.??
     

Share This Page