Briggs 18HP I/C runs rough (only when hot)?

Discussion in 'Mechanic and Repair' started by PJDiesel, Aug 20, 2006.

  1. PJDiesel

    PJDiesel LawnSite Member
    Posts: 146

    I recently acquired an older Yard Man with and 18HP I/C full pressure lube Briggs.
    Here’s the deal. It runs SWEET when you first start it cold, little bit 'o choke to get her going, runs up through the RPM range nicely, idles real smooth, drives and cuts 100%.

    5-7 minutes later..................

    Runs like crap, almost dies out completely, revs, dies, revs. It runs fair when it is at about 3/4 throttle, horrible at idle.

    Let it cool for 1/2 an hour or so, runs like a top again (for a few minutes).

    I've had the carb apart, totally blown out & cleaned. All seems well with the fuel supply, new filter, and fresh fuel.

    It's a very clean mower for its age, hydro and all! It's a real shame it is acting up like this..
    Any thoughts?
  2. PJDiesel

    PJDiesel LawnSite Member
    Posts: 146


  3. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    When it starts running bad check spark on both cylinders by removing each plug wire one at a time and see if it dies, Sounds like the coil heating up and breaking down.
  4. PJDiesel

    PJDiesel LawnSite Member
    Posts: 146

    Thanks Rob, I'll give it a try.

    'member me? I'm the guy you helped with the Turf Tracer I bought used in the spring? Still runs like a champ!:clapping:

  5. PJDiesel

    PJDiesel LawnSite Member
    Posts: 146

    Okay. First of all, BOTH sides light my monkey ass up when I tried to pull them. :dizzy: My son got a kick out of it...........

    Passenger (starboard side sitting in the seat) side didn't do a thing when I pulled it off. Drivers side killed it like someone shut the key off.

    Is the going to be mounted near the flywheel? There is a little black box mounted on the outside of the top engine cover, it has a two sire harness comming off of it and a wire to the lights, whats that?!
  6. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh:
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    [​IMG] [​IMG] Sorry Phil :hammerhead: I just assumed you knew they would get ya and use rubber coated pliers.

    That sounds like the voltage regulator you described, The coil is under the top cover. You can't MISS it, Also when you install the new one use any business card to set the air gap or a .010 feeler gage.

    Sorry Again Dude.....
  8. PJDiesel

    PJDiesel LawnSite Member
    Posts: 146

    No problem, it was a....well,.... EXCITING experience.:dancing:

    Funny thing is I didn't learn from the first side, I had to go and do it on the other one too!:hammerhead:

    I'll slap a new coil in there tomorrow afternoon and see how she acts.

    Thanks for the tips.
  9. PJDiesel

    PJDiesel LawnSite Member
    Posts: 146

    You know what they say about assumptions don't you?!

  10. lucforce

    lucforce LawnSite Member
    Posts: 223

    If you replace the magnetron on this thing, I suggest that you replace the ignition switch as well. The switches have been found to aide in the demise of the magnetron ignition while still appearing to function normally.

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