Honda GX620 20HP cutting off...

Discussion in 'Mechanic and Repair' started by jomeokee, Dec 3, 2012.

  1. jomeokee

    jomeokee LawnSite Member
    Posts: 48

    I have a Honda is a 10kW welder/generator that sees infrequent use.

    I tried to start it today and let it run. No luck so I guesses that the card was gummed up. I keep it dosed with Sea-Foam and after pulling the carb and opening it up I find that it was very clean.

    Here's what I tested for:

    1. fuel pump,OK
    2. Spark, OK
    3. Float and needle, OK

    I was unable to unscrew the main jet. The brass jet was very hard to break so I left it in after blowing on it and getting air to pass.

    I reassembled the carb and the engine fired with the choke. After playing with the choke the engine decided to run with the choke in the off position.
    I thought the problem was solved, this machine had sat longer than normal and I guessed some fresh gas solved the problem.

    Wrong, after a minute or three she cut off.

    There is a fuel solenoid on the bowl that kills the fuel. I need to test for power when the engine cuts off.

    The oil measures a little low but until I fill it up to the top I will not know if oil may be the culprit.

    Anyway, I was brain storming and in hopes some LS engine gurus might be able to shed some light on something I am missing.

    Thanks in advance,

    Tom
     
  2. robert@honda

    robert@honda LawnSite Member
    from Atlanta
    Posts: 138

    Honda GX620; got a serial number? I can look up service information (troubleshooting, service bulletins, etc.). Should be on the side of the block and in the form of "GCAD-1234567" or "GCARK-1234567" (gasoline models).

    Bulletins for the all GX620's include:
    Ignition Coil Air Gap (1994)
    Engine Misfire / Hard Restart (1996)
    Cold Starting (1998)
    Recurring Spark Plug Fouling (2004)
    Camshaft Replacement (2001)
    Improved Valve Lifter Assembly (2001)
    Low Oil Pressure (2007)

    -Robert@Honda
    Caveat: I work for Honda, but the preceding is my opinion alone.
     
    Last edited: Dec 4, 2012
  3. jomeokee

    jomeokee LawnSite Member
    Posts: 48

    Robert,

    Thank you very much! I am at whits end on what is going on.

    The number is:

    VXE8 this number is directly above the lower number. Thermadyne may have placed that number there?
    GCAD 1040268

    Thanks again,

    Tom
     
  4. robert@honda

    robert@honda LawnSite Member
    from Atlanta
    Posts: 138

    Based on the serial number, there are no active service bulletins for it, nor do any of them point to a "shuts down after running okay for a while" problem.

    Let me query our Tech Line guys and see what they say. Hang on.

    -Robert@Honda
    Caveat: I work for Honda, but the preceding is my opinion alone.
     
  5. robert@honda

    robert@honda LawnSite Member
    from Atlanta
    Posts: 138

    Okay, here's what our tech guys say:

    1. When you tried to remove and clean the main jet, spraying air/cleaner into it may have impacted the possible debris/gunk into the emulsion tube. See part #14 on the attached drawing. So, that main jet and emulsion tube should get removed and cleaned, along with a complete cleaning of the entire carb. As a new carb is $192 list (yikes), you may wish to have a Honda engine dealer do an inspection first, then it's on them to get the engine running correctly.

    2. FYI, the fuel cut solenoid works opposite what you'd think on other engines:

    First, it get a steady +12V from the genset when the engine is running, but the ground is not connected, and the unenergized position of the plunger on the solenoid is retracted.

    Next, when you turn the engine OFF, a ground (-12V) is sent to the solenoid, causing it to extend and block the fuel from flowing through the main jet. It stays in this position until the genset stops supplying +12V to the solenoid, then the plunger retracts.

    So, it's less of a "fuel cut solenoid" and more of a "backfire prevention device." If the main jet were to continue getting fuel during engine shutdown, it's likely there would be a backfire through the muffler.

    Hope this helps, Mike. Here's a link to find the nearest Honda Engine Dealer:

    Honda Engine Dealer Locater

    Here's the image of the carb from the parts catalog (attached).

    -Robert@Honda
    Caveat: I work for Honda, but the preceding is my opinion alone.

    GX620K0 CARBURETOR.jpg
     
  6. jomeokee

    jomeokee LawnSite Member
    Posts: 48

    Robert,

    Thank you fellow!

    Let me did into this and I will report back.

    Tom
     
  7. jomeokee

    jomeokee LawnSite Member
    Posts: 48

    Robert,

    I was unable to break the brass main jet screw. I was using the largest driver and still couldn't get to break. I am going to take it apart again and soak it in PB blaster and see if that gets it. The main jet has got to have some very small pieces of trash. The engine will runs w/o choke and then it dies.
     
  8. jomeokee

    jomeokee LawnSite Member
    Posts: 48

    I have always been told in trouble shooting mechanical issues to look for the most obvious things first.

    With this engine I didn't do that. Being a welder/gen set I automatically thought the carb/bad fuel was the issue.

    Wrong!!!! I had the carb apart 2X and it was perfect. I added oil, still would run then die.

    Finally I thought the Mikuni fuel pump was the issue. I go to remove it and there before my eyes is a very rotten fuel line that was let air enter.

    Some new Tygon hose and the Honda is back to purring like a kitty!

    Thank you Robert for the help!
     

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