Briggs Stratton surging problems

Discussion in 'Mechanic and Repair' started by bsbretly, Sep 15, 2009.

  1. bsbretly

    bsbretly LawnSite Member
    Posts: 19

    I have a BS 135202 with a pulsa jet tank mounted carb on my go-kart. The engine was "surging" or "hunting" at full throttle. I would be at full throttle and it felt as the throttle was temporarily released (which it wasn't) then it would immediately retain full power. This process would repeat intermittently. I disassembled the entire carb and soaked it for 30min in chem-dip carb cleaner, hit all the jets with compressed air, and got rid of all visible dirt. I reinstalled the carb with new gaskets and the problem persists. Any ideas? I thought it could be fixed with adjustment of the idle mixture screw, but that didn't seem to help. Please let me know what the issue could be. Thank you.
     
  2. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Posts: 1,276

    Is this your carburetor?

    [​IMG]
     
  3. bsbretly

    bsbretly LawnSite Member
    Posts: 19

    Yes that is it.
     
  4. bsbretly

    bsbretly LawnSite Member
    Posts: 19

    I used that very same diagram in order to disassemble the carb
     
  5. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Posts: 1,276

    That's the same carburetor I have on my 3.5HP Briggs horizontal shaft. 127 and 127A are welsh plugs. It's probably not critical to pull the big one off the back, but the small one--> 127A should probably be pulled. I had the same problem that you're experiencing, and the mower shop owner told me to pull both those welsh plugs off and clean the holes behind them with a set of torch tip cleaners. Best advice I've ever gotten from a mower shop and it worked!! Well, only the small welsh plug has two small holes behind it and that's the one you want to pull. You can replace both of them if you want to - they're only a couple of dollars.

    Those welch plugs are dome shaped to make them springy. When you install them by punching the center of them with a large center punch, right smack in the middle of them, they spread out and grab the recess permanently. Use a large center punch that's not too sharp so you don't punch through it.

    If the big plug in the back is sucking air in around the rim of it, you can seal it up with clear finger nail enamel. Mine wasn't sucking air at 127, but 127A had one of the holes behind it block with corrosion.

    If I remember correctly, behind the welsh plug is a brass jet with a large hole in it -- remove that jet by unthreading it with a screwdriver and you'll see the 2 small holes behind it that I'm talking about.
     
    Last edited: Sep 16, 2009
  6. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Posts: 1,276

    By the way, if the wire doesn't enter the hole fairly easily, select a smaller wire. You don't want to enlarge the hole, just remove the white deposits blocking the flow of fuel through it.
     
  7. bsbretly

    bsbretly LawnSite Member
    Posts: 19

    I see, thanks. Do you have to pull the entire carb back off or can you get out the welsh plug while the carb is still bolted to the tank?
     
  8. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Nice of you to add that ! Thumbs Up

    BTW, There's no jet behind 127A.......
     
  9. bsbretly

    bsbretly LawnSite Member
    Posts: 19

    So one of you is saying there are jets behind the small welsh plug (127a) and the other says there are no jets behind it. Which one is it? Also, how are these welsh plugs removed?
     
  10. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Posts: 1,276

    Then what's behind it? Maybe I'm thinking of the other carb with the single pick up tube. I've been through so many carbs I've lost track. :confused:

    Wait!! I think its coming back to me.... there's 2 holes that lead to a passageway to the diaphragm chamber, correct?
     
    Last edited: Sep 17, 2009

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