Briggs motor woes

Discussion in 'Mechanic and Repair' started by Central Island Lawn, Oct 27, 2011.

  1. Central Island Lawn

    Central Island Lawn LawnSite Member
    Messages: 50

    Hi all
    I picked up a very inexpensive Snapper Rider. It's small, 25" cutting deck, but it's a really fun machine and the smaller size is easy to get in to smaller spaces and it turns on a dime. It's an older unit and the 6 HP Tecumseh was a POS, and I can't get parts for it anymore, so I picked up a used 12 HP Briggs motor for about $200. I have this problem where the engine will start great when cold, run for about 30 to 60 seconds. Then the governor will take over and start adjusting the throttle, engine RPMs will drop and eventually the motor will cut out. The carburetor that was on there would leak fuel, even with a new carb kit, so I replaced the carb. I've also replaced the ignition coil, spark plug, and re-wired the starter. What I have not done is hook up the alternator to the battery, which shouldn't make a difference other than recharging the battery. I also have not replaced the air filter, which seems a little too obvious. I'm going to replace the air filter tomorrow, but I wonder if there is something else that I should consider. The engine does get hot fairly quickly and that is when it shuts off.


    PS. The mower cost me $200, $200 for the engine, and $200 for a new carb.
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    $200 for a carb ? Dayum !

    Can you post the engine model and type numbers ?
  3. Central Island Lawn

    Central Island Lawn LawnSite Member
    Messages: 50

    The engine model and type is:
  4. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Messages: 2,249

    What the code number--the last of the three engine numbers. The first two digits of the code will indicate the year of manufacture. Judging from the carb on that engine, it's likely an early to mid 90's engine or possibly earlier.

    A used engine is most always a gamble unless you know it's history, observed it run or have done some elementary testing.

    Unfortunately, the train has already left the station and you've got $400 wrapped up in an engine that isn't doing the job.

    Where to start?

    Check the compression, cold and hot. Low compression could mean several things--valve problems, cylinder/ring wear, head gasket leak

    Adjust the governor properly.

    Check for any possible intake leaks.

    Don't spend any more money on it until you know it can be made satisfactory within the limit you can afford to invest. Internal engine work can get pricey unless you can perform the work yourself.

    Just a few random and elementary thoughts. Rob/others will likely come back with some additional suggestions as well.

    Good luck.
  5. Central Island Lawn

    Central Island Lawn LawnSite Member
    Messages: 50

    Something I would like to add:
    I just ran it. It started great, first crank all the time without any choke on low throttle. I left it to run at idle, once it warmed up it was a little rough but kept running. It didn't die until I added throttle and let it run at full throttle for a few seconds. Running at lower throttle seems to be okay though.
    What are the chances that it's the air filter?
  6. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,337

    What does the sparkplug look like?
    Clean or oily or black and sooty?
    Posted via Mobile Device
  7. jdunk

    jdunk LawnSite Member
    Messages: 20

    carb issue out of ajustment starts with out choaking running rich idel circuit?

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