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  1. #1

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    installed a head on another jet ski, low compression

    I installed a rebuilt head, local machine shop, on a 2003 gtx, after putting the good valves in. I tested compression right after and it was 100 110 120 I dont understand the 1503 marks were perfect and i used the right tools and locked everything in place. I ran it for 5 seconds and it sounded good. My battery is older but i dont know if it cranks over slow or fast. I have had a lot of problems with another ski of mine and hope i dont have issues with this one too, thanks.



  2. #2
    mac_man_luke's Avatar
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    You have a few possible issues:

    1) Compression tester is faulty, try another
    2) Battery being old and flat will affect readings.
    3) Valves might need some time to bed in (although they should have been lapped in)
    3) More major issue with rebuild.

  3. #3
    monaroman76's Avatar
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    Was the engine warmed up when you checked compression?

  4. #4

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    stone cold, seems a little low on oil, bottom of the range, so i have to add some before i warm it up i assume. The same ski before getting the new valves had 130 across the board no issues but the 72 valves so i hope i made a good decision putting the 75 valves in.. He cut them and the seats and installed them. He being machine shop guy.

  5. #5
    monaroman76's Avatar
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    Quote Originally Posted by lemon4879 View Post
    stone cold, seems a little low on oil, bottom of the range, so i have to add some before i warm it up i assume. The same ski before getting the new valves had 130 across the board no issues but the 72 valves so i hope i made a good decision putting the 75 valves in.. He cut them and the seats and installed them. He being machine shop guy.
    Get it to operating temperature and do another test if you are worried. I'm betting that it will be okay.
    Possibly the valves still need some running time before seating 100% correctly.

    If your compression was good before, I am sure you will be fine.

  6. #6

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    Im just hoping i didnt mess up the gasket, everything torqued correctly (stretch bolts, new ones) and i checked them at 80 ft lbs and the didnt move. I dont think he lapped them. I watched him just put the in. I think he cut them slightly for a smooth angle though. Lapping you use an abrasive compound and spin it right? And i put 1211 on moderately. A little seeped out but not much.

  7. #7
    formerly Gold06RXP Turbo Nick's Avatar
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    Take it out and run it then recheck. Your comp will be low after a valve job

  8. #8

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    Ok thanks!!!! i was so worried, im not out of it yet but it seems its typical after the valve job he did.

  9. #9

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    well before i ran it in the ocean i ran it on the hose and it reved to 4k ( i gave it a little throttle, not much) and it got stuck at 4k and throttle cable wasnt stuck

  10. #10
    speedskixp's Avatar
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    Did you lock the cam bolts down before or after installing the chain tensioner?
    Second issue sounds like a sticky throttle body.

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