Stumped! FH680V problem

Discussion in 'Mechanic and Repair' started by shane772, Aug 15, 2019.

  1. shane772

    shane772 LawnSite Member
    Messages: 201

    Motor is running good for 20-30 minutes then starts searching for rpm's. No change when I put on choke. Compression is 90psi in both cylinders (cold), bumps 3-5 psi with a squirt of oil in the cylinder. With this, I assumed it was electric since it didn't change with choke on and compression is well within range. Put 2 new coils and plugs, no change. Cleaned fins etc under shroud, no change. Beginning of the season I put on a new carb, maybe I should put the old one back on and see if it changes??? Any ideas as to what to check next?
     
    Last edited: Aug 15, 2019
  2. fatboynormmie

    fatboynormmie LawnSite Bronze Member
    Messages: 1,439

    Try loosening the gas cap when it starts acting up. If it straightens out you have a clogged breather on the cap . Could also be the pick up tube inside the tank could be sucking air or is damaged due the ethanol. My .02
     
    Ridin' Green likes this.
  3. OP
    OP
    shane772

    shane772 LawnSite Member
    Messages: 201

    I tried loosening the cap with no change. I've used non ethanol since new. Thank you for the input.
     
  4. Skeeterman

    Skeeterman LawnSite Member
    Messages: 85

    Could be ignition module or stator.
     
  5. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Messages: 21,622

    Could be a coil going bad and as it heats up it starts acting up, which would explain why you can run for a while before it acts up.
     
  6. OP
    OP
    shane772

    shane772 LawnSite Member
    Messages: 201

    Ridin' Green, put 2 new coils on yesterday. Coils that were on it are only 2 months old too. Plugs look good and was getting spark from both.

    Got up early and changed the carb. No change. This morning it was dark so mower was sitting still with blades on and had exact same problem. Once engine gets hot, starts searching and rpm's going up then down, repeat until it dies.
     
  7. hal

    hal LawnSite Bronze Member
    from Georgia
    Messages: 1,674

    How old is this engine? Your governor spring may be getting weak. Also your oil may be too thin.
     
  8. Turf Tracer

    Turf Tracer LawnSite Fanatic
    Messages: 5,251

    Check not moving back to choke position. Had this on few FS engines. Spring on choke was defective. There was dealer recall
     
  9. OP
    OP
    shane772

    shane772 LawnSite Member
    Messages: 201

    1000 hrs on engine .Tried changing fuel filter, drain fuel and checked for water and also ran off a sepersepfuel source all with no change. Now I have to go get my route done with 1 mower, gonna be a long day! Lol
     
  10. hal

    hal LawnSite Bronze Member
    from Georgia
    Messages: 1,674

    Check your governor linkage or other electrical components, it is heat related, baffles clean, valves correct... What unit is it on?
     

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