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Briggs running poorly

Discussion in 'Mechanic and Repair' started by New Bern Bear, Apr 29, 2008.

  1. New Bern Bear

    New Bern Bear LawnSite Member
    Messages: 20

    Good morning all ... I bought a 11 yr. old MTD with a 14.5 hp commercial briggs at an auction for $50.00. Got the engine running in 1.5 hrs. It has not been run in 4-5 yrs. anyway by the look and smell of the gas.

    - changed the oil and put in some LUCAS Oil treatment
    - Flushed the gas tank
    - replaced the fuel line and filter
    - Cleaned out the bowl on the carb. and fuel flows nicely.
    - Installed a new battery
    - replaced air filter.
    - Added carb cleaner to the new gas and ran for an hour.

    Needs a spindle and I will have a mower for homeowner use.

    Question is, Engine runs great with the choke at about 1/2 on.... back fires and runs poorly with choke off.

    Any suggestions ...

    I have tried carb cleaner down its nech while it was running ... nothing.

    My thoughts are that the carb. must still have varnish or grim plugging it up. What do you guys think?

    I would appreciate your thoughts,

  2. Tom Tom

    Tom Tom LawnSite Bronze Member
    Messages: 1,281

    carb pickup tube or needle jet may have partial blockage
  3. action13

    action13 LawnSite Member
    Messages: 29

    Sounds like it's starving for gas. Taking into consideration you have no air leaks and installed new gaskets, and have after a warm up readjusted the high speed, and idle. I would pull the carb again, and then soak it in a good parts cleaner for about 30 minutes. Unless you have access to a ultrasonic parts cleaner. Remove all jets and needles, remove the bowl, needle valve, and float. After soaking pushing some carb cleaner through each and every circuit. Make sure the cleaner goes in and comes out ever path. Blow out each path with compressed air. When these have been really gummed up good it takes some doing to clear the passages sometimes. They say never us a wire to clean the passages, but I do 10 times a week, If you use a wire you should have various sizes, DO NOT USE a wire to big and change the size of the hole!! Be gentle with it. Look for holes in the bowl nut that has become blocked. One tiny little missed passage will cause you headaches till you find it. Assuming you used new parts, check your float height, and reassemble. Set your main or high speed screw screwed in till it just bottoms, then back out 1 1/2 turns, then the idle or low speed the same way but 1 turn backed out, warm it for 5-10 minutes and readjust buy turning it clockwise till it just starts to run rough (go very slowly, allowing the engine to adjust to the new mixture) then turn it back clockwise till it runs rough again, then setting it to the midway point of the two points. Then do your low speed the same way. Best to have your air cleaner installed during the adjustment to simulate a true running condition......Tom
  4. New Bern Bear

    New Bern Bear LawnSite Member
    Messages: 20

    Ok fellas,

    - I have removed the carb.
    - Cleaned it inside and out.
    - Put it back on with new gaskets.
    - Mowed my lawn with chock half way on
    - Still having the same problem when I take the choke off

    - Runs excellent and mowes vary well with the choke 1/2 on.
    - should I worry or just say the heck with it and run it. Perhaps it will run its course or clean itself out with some use.
    - It cut my 1 acre lawn without a hitch

    Aggravated and confused
  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Post the model and type numbers off this engine so I can see which carb you have......
  6. Tom Tom

    Tom Tom LawnSite Bronze Member
    Messages: 1,281

    Did you remove the needle jet?, or just squirt something up the tube to try and clean it out?

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