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2007 gt125r compression test

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    • Oct 9, 2024 at 3:34 PM #15127
      Brian
      Participant

      Done a compression test on my 2007 gt125r, had the bike up to temperature before test,full throttle and charges battery, readings are 135 on each cylinder, the spark plugs are also fouling/black and sooty. Are these readings OK or should this merit further investigation? I would hope it was just an over fueling issue so I wouldn’t  have to strip the engine down. Thanks

    • Oct 9, 2024 at 5:24 PM #15131
      â™ ï¸ M77
      Keymaster

      Warm up the bike again,

      Then remove both spark plugs , crank at full throttle for 5 seconds

      And tell us the readings again in PSi if possible.

      Regards

    • Oct 10, 2024 at 11:58 AM #15140
      Brian
      Participant

      So I got the engine hot and tested again. Psi was 125 each cylinder, I seem to loose 10 psi per cylinder when hot.

    • Oct 10, 2024 at 2:27 PM #15141
      Brian
      Participant

      I really should mention the bike was on its side when it was delivered,so oil could have made its way up into the cylinder,  the rear cylinder is 100 percent burning oil. I just don’t understand why the compression readings are the same in both cylinders.

    • Oct 10, 2024 at 6:49 PM #15144
      â™ ï¸ M77
      Keymaster

      Burning Oil = Piston Rings . Scored Barrels ,  or  Valve SEATS dripping oil in to piston chambers  (hence probably sooty plugs)  or simply rings on the way out with the barrel.

      125 psi = You’re literally at the limit as to what hyosung considers a time to rebuild engine.   Generally 150-175 psi is expected.

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FORUM ARCHIVE: Boards are now read-only as archives. For bike service manual downloads, parts shop, or to read more about the forum changes, tap here to read more....
Viewing 4 reply threads
  • Author
    Posts
    • Oct 9, 2024 at 3:34 PM #15127
      Brian
      Participant

      Done a compression test on my 2007 gt125r, had the bike up to temperature before test,full throttle and charges battery, readings are 135 on each cylinder, the spark plugs are also fouling/black and sooty. Are these readings OK or should this merit further investigation? I would hope it was just an over fueling issue so I wouldn’t  have to strip the engine down. Thanks

    • Oct 9, 2024 at 5:24 PM #15131
      â™ ï¸ M77
      Keymaster

      Warm up the bike again,

      Then remove both spark plugs , crank at full throttle for 5 seconds

      And tell us the readings again in PSi if possible.

      Regards

    • Oct 10, 2024 at 11:58 AM #15140
      Brian
      Participant

      So I got the engine hot and tested again. Psi was 125 each cylinder, I seem to loose 10 psi per cylinder when hot.

    • Oct 10, 2024 at 2:27 PM #15141
      Brian
      Participant

      I really should mention the bike was on its side when it was delivered,so oil could have made its way up into the cylinder,  the rear cylinder is 100 percent burning oil. I just don’t understand why the compression readings are the same in both cylinders.

    • Oct 10, 2024 at 6:49 PM #15144
      â™ ï¸ M77
      Keymaster

      Burning Oil = Piston Rings . Scored Barrels ,  or  Valve SEATS dripping oil in to piston chambers  (hence probably sooty plugs)  or simply rings on the way out with the barrel.

      125 psi = You’re literally at the limit as to what hyosung considers a time to rebuild engine.   Generally 150-175 psi is expected.

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