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  1. #1

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    Drop in compression

    Just checked the compression on my 01 gp1200r middle and rear cylinder 145 the front was at 135 I know they are suppose to be withn 10 percent of each other. But last time I checked they were all at 145 and I have put about 2hrs on it since I last checked which was last year at the end of the season


  2. #2

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    Little background on the motor. I rebuilt it in 2010 and put about 30 hrs on it last year only about 2 this year

  3. #3

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    Ok took the heads off And I made sure the power valves were working and I found out that 2 screws that hold the valve to the bar that turns had come out. On the middle and rear cylinder
    Front Cylinder 135 PSI



    Middle 145PSi



    Rear 145PSI




    Heads
    Front/Middle/Rear


  4. #4
    Yamaha artisan Cutlass's Avatar
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    Not much piston wash on the front and middle cylinders so they are running lean it seems. If its lean, it could be overheating the piston and rings and that could explain you lower compression. Just a thought...might not be the root cause of your problem.

  5. #5

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    Should I look into replacing the front piston and clean the carbs.

  6. #6
    Yamaha artisan Cutlass's Avatar
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    I'd probably inspect it and post some pics. Pull the cylinder off.

  7. #7

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    Will do

  8. #8

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    How does the rear cylinder look?

  9. #9

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  10. #10
    thats the front piston? right? what does the cylinder look like? why did you have to rebuild last time? full rebuild or just top end? who's parts did you use? sleeves or reniked the cylinders? did you disconnect the PV servo while perfoming the compression check?

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