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New Guy with '77 GS400X running problems

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    New Guy with '77 GS400X running problems

    Hey folks, New guy here from the west coast (of New England... Burlington, VT ) with a slightly lame 1977 GS400X on my hands. I picked it up for a good deal from a guy 50 miles away from me- got it running at his house and was able to ride it home. However, the next day I couldn't get it running again. I had a local bike mechanic clean and rebuild the carbs and I installed a new battery. He said the points were slightly pitted and the condenser may need replacing.

    Currently I can get it running, but only on the right cylinder. The left is totally dead, it makes no difference whether the spark plug wire is on or off the plug. I inspected the points- they both had a discolored circle in the middle, surrounded by shiny metal. I filed them a little bit, cleaned them thoroughly, and gapped them to the tolerances in my Clymer's manual. When I kickstart it, still only the right-hand cylinder is operational. I can see sparks in both of the points when they open, so I'm not sure why the left one wouldn't be working. Am I missing something really obvious? Anything specific I should be looking for or checking?

    It's finally nice again today after a weekend of rain, so I will be out there troubleshooting to the best of my abilities. I really don't know much about classic bikes, I'm used to modern EFI systems so any help in this matter would be very much appreciated. Thanks for looking!

    Ride safe,
    dpatlak

    #2
    Welcome to the forums.
    Try leaving the spark plug in the LH cylinder, remove the cap and insert a spare spark plug into the cap and ground the side of the plug on the cylinder head. Start it up. Got a nice fat blue spark? If so, you may have a fuel problem or mechanical cylinder issue. Have you talked to the local bike mechanic? Was it running on two when you picked it up from him? How long ago?

    Comment


      #3
      Thanks for the reply! Yeah, I haven't gotten around to testing the spark plug yet- It's a strange size (18mm?) that I didn't have a deep socket for. The guy who rebuilt my carbs says he could get it running, but it wasn't holding an idle. That is exactly the issue I'm having, so I don't think it was ever running on 2 cyl after he had it. That was maybe a week or two ago. I'm pretty sure it was running on both when I rode it the 50 miles, unless these things will ride at 55mph+ on only one cylinder...

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        #4
        As mentioned when did it start running on 1 hole?
        How many miles on the bike?
        How long has it been sitting?
        "a local bike mechanic"...nearly swear words around here
        Compression test done?
        If you have spark you'll have fire (Unless no fuel). If no spark sway a Dayna set up in it.

        Welcome to the fourm. There is a roll of carpet around here with your name on it!

        Dave

        Comment


          #5
          Originally posted by Dave8338 View Post
          As mentioned when did it start running on 1 hole?
          How many miles on the bike?
          How long has it been sitting?
          "a local bike mechanic"...nearly swear words around here
          Compression test done?
          Started running on one cyl after the new battery got installed and the carbs rebuilt.
          It has 17,xxx miles I believe, the previous owner said he had it running end of last season but it had been sitting all winter, and now it's been sitting at my place 2 weeks or so.
          No compression test done, that's the next step if the issue isn't electrical...

          Thanks!

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            #6
            I'de start with the carbs again if I were you...

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              #7
              erk... if it's the carbs I'm going to give my bike guy hell. Like I said, I'm new to classics and carb'd bikes in general- I gotta learn how to rebuild my own!

              Comment


                #8
                Originally posted by dpatlak View Post
                erk... if it's the carbs I'm going to give my bike guy hell. Like I said, I'm new to classics and carb'd bikes in general- I gotta learn how to rebuild my own!
                YUP! That way you'll KNOW that it was done right! OH...did I mention the money it saves...

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                  #9
                  Well, it might turn out to be nothing but faulty plugs. Tested the left-hand spark, it was working but pretty weak. The right-hand was better, but both plugs were badly fouled. Got some new ones, about to install them and see how it goes!

                  Comment


                    #10
                    Ya didn't tell me that you had an old set of plugs in the thing!

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