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  1. #1

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    Thumbs up How to do a Compression Test

    When testing compression : Cold engine: Be sure your battery is good and fully charged to max befor testing, Remove all 3 plug wires and store them safely away from the engine area and be sure there is no gas or fumes in hull, remove only on sprakplug at a time ( leave the other two in when testing ) Un plug electrical power valve servo motor, be sure power valves are closed, hold throttle full open when testing, record gauge reading, repete test again on same cyl. just to get a good reading, then do the same on the other two cyls. If you battery seams to slow down during testing re charge battery between each cyl. test , This is the only way to do a good compression test IMO, Tommy Jordan


  2. #2
    canadaxp's Avatar
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    Quote Originally Posted by 2fast4u View Post
    Un plug electrical power valve servo motor, be sure power valves are closed
    Question, what difference would this make in the final comp if one did not do this? I am assuming it would bring it up a bit?

  3. #3

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    Quote Originally Posted by canadaxp View Post
    Question, what difference would this make in the final comp if one did not do this? I am assuming it would bring it up a bit?
    ON my 2000 gpr when you are doing a compression test the power valves will cycle open then close. I un hook the servo to be sure I get a constant reading and record this info and save it for future information so I can check my motor to see if It it still good to go or that the compression has started to go away for some reason, I usualy see 3 -6 psi higher with the power valve servo un hooked and valves down. Keeping a good data log of information on your motor when its fresh ( In good working order) helps you later when you supect something might be going wrong with your motor, Tommy Jordan

  4. #4
    Moderator OsideBill's Avatar
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    Great post Tommy, I copied it and made it a "how to"

    this test applies to all 2 stroke skis, if you do not have power valves ignore that portion.

  5. #5
    If your not doing something, its hard to screw up. stlouisramsfan's Avatar
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    Quote Originally Posted by OsideBill View Post
    Great post Tommy, I copied it and made it a "how to"

    this test applies to all 2 stroke skis, if you do not have power valves ignore that portion.
    When i read this last night, i thought it should be "stuck"
    thanks

  6. #6
    Hybrid AWD's Avatar
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    I'm getting ready to go look over a GP1300R this upcoming Wednesday and I was just reading over the manual and seeing what I could find online about things to look for and I cam across a conflict between here and there.

    In the manual it says to remove all of the spark plugs instead of just one at a time. What is the reasoning as to why you recommend to leave one out at a time?

    Also, why do you recommend disconnecting the PV servo?

    Lastly, what is the benefit to doing a cold reading vs. warmed up (118* F) as the manual says?

    I'm not questioning your method, just trying to make sure I do it properly and get accurate readings the right way. Thanks.

  7. #7
    steach's Avatar
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    Quote Originally Posted by Hybrid AWD View Post
    Also, why do you recommend disconnecting the PV servo?
    This ensures that they all stay closed while turning the starter (consistancy).

    What year 1300R? The 2005+ dont have power valves.
    Follow the directions above. The key is having a FULLY charged battery.

  8. #8
    Hybrid AWD's Avatar
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    Quote Originally Posted by steach View Post
    This ensures that they all stay closed while turning the starter (consistancy).

    What year 1300R? The 2005+ dont have power valves.
    Follow the directions above. The key is having a FULLY charged battery.
    It's a 2003 GP1300R. I'm gonna send the guy an email asking him to make sure the battery is fully charged.

  9. #9
    Kid In A Adult Body sandman7793's Avatar
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    Why in the yamaha manual does it say the compression on a 2001 xlt 1200
    is 500 kpa on a tester that equals around 72 psi and my cylinders are around 110 psi which i think is kinda low ANY HELP

  10. #10
    steach's Avatar
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    Quote Originally Posted by sandman7793 View Post
    Why in the yamaha manual does it say the compression on a 2001 xlt 1200
    is 500 kpa on a tester that equals around 72 psi and my cylinders are around 110 psi which i think is kinda low ANY HELP
    The spec in the manual is for a minimum compression. 110 is a tick low but if its consistant you should be alright

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