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  1. #1

    Fresh rebuild....now knocking

    I just rebuilt my Xl1200's 3rd cylinder due to low compression.
    I started it just now on the hose and about every 10 seconds you'll hear a knock.
    Then 10 seconds after that, you'll hear another knock or 2.

    I haven't broken it in yet, I just started it on the hose, heard this and stopped.
    I started it a couple more times and it SEEMED to knock less around idle. When I revved it a bit, it knocked thought.

    I took a compression test and it was 105,100,100. (Conditions: hot engine, throttle wide open)


    any help is appreciated,

    Tom


  2. #2
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by tejhummer View Post
    I just rebuilt my Xl1200's 3rd cylinder due to low compression.
    I started it just now on the hose and about every 10 seconds you'll hear a knock.
    Then 10 seconds after that, you'll hear another knock or 2.

    I haven't broken it in yet, I just started it on the hose, heard this and stopped.
    I started it a couple more times and it SEEMED to knock less around idle. When I revved it a bit, it knocked thought.

    I took a compression test and it was 105,100,100. (Conditions: hot engine, throttle wide open)


    any help is appreciated,

    Tom
    did you inspect crank when you rebuild it.

  3. +1 by:

    WFO

  4. #3
    I didn't take all the cylinders off, just the 3rd. I looked at the crank and it looked fine.

  5. #4

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    Was the piston on the #3 cylinder 100% intact? Reason I ask is because my dad bought a gp1300r at the beginning of the year that the previously owner only replaced the number one cylinder and piston due to water ingestion. It had a similar knock and he couldn't figure out why it was making a noise when he fired it up on the trailer. What I found when I tore the motor down was that a side of the piston skirt had broken off and the noise we were hearing was the piston skirt piece rattling around inside the motor.

  6. #5

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    Jim may be right about the crank because on my motor, the noise was constant whereas yours happens every 10 seconds or so.

  7. #6
    The piston looked fine, I thought actuall I remember this sound before the rebuild as well.

  8. #7
    What would the cranks problem be?

  9. #8

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    Quote Originally Posted by tejhummer View Post
    What would the cranks problem be?
    Possibly the bearings..

  10. #9
    I never touched the crank though..

  11. #10
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by tejhummer View Post
    What would the cranks problem be?
    possible rod bearing, rods tend to give a knocking sound.

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