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  1. #1
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    951 stock Compression??

    Hey guys i have a 98 GTX 951 with 120 psi and 121 psi is this low where should it be what is stock psi????


  2. #2
    It is a bit low but CONSISTENCY over both cylinders is whats more important so your ticking that box

    Im pretty sure a fresh motor will test around 150/140 psi.

  3. #3
    mibunkerking's Avatar
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    150 is stock compression. however, there is a chance that your gauge is inaccurate. usually if they are 130+ and EVEN, your good to go. but 120, even on a shady gauge is low. i cant imagine it being off by 30psi. test it on another gauge and see what it comes up with.

  4. #4
    KrunchovXPL-GTX-RX's Avatar
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    A weak starter and or battery can cause it to read low too.

    As Kid said, you look for little or no variance so you are good there. If you are worried about your total compression then do as King says and try another gauge. I would get a good charge on the battery to eliminate that as a possible issue.

  5. #5
    96XPSS's Avatar
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    Change the schrader core on your compression gauge and see if the numbers improve.

  6. #6
    KrunchovXPL-GTX-RX's Avatar
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    That is assuming that you are using a screw-in type gauge and not one of those rubber stopper type things that you are supposed to hold up against the plug hole.

    Those things are about as accurate as a super market tabloid.

  7. #7
    When I bought my 98 GSXL back in 98 compression was 130 in both cylinders.

  8. #8
    Kidd800XP's Avatar
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    I guess I am just a dumb azz cause I always thought that stock compression was 130

  9. #9
    Quote Originally Posted by mibunkerking View Post
    150 is stock compression. however, there is a chance that your gauge is inaccurate. usually if they are 130+ and EVEN, your good to go. but 120, even on a shady gauge is low. i cant imagine it being off by 30psi. test it on another gauge and see what it comes up with.
    Not true, stock compression for a 951 is in the neighborhood of 130-135 psi.

  10. #10
    KrunchovXPL-GTX-RX's Avatar
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    This comes up every time someone asks about the stock comp on a 951 which is why I try to talk about the variance rather than the gross reading.

    I have an '02 that has never been apart and with almost 200 hours it still pumps 150+ in both cylinders (on three different gauges). Most of the stockers I have built hit 140 right off the bat. If you go on another site (cough seadoo.net cough) the official line is more like 150. There are, however, a number of guys who see the stock comps in the 130 range on perfectly good engines.

    So... I am not saying that anyone is wrong, but to me, with my gauge, where I am in the country, I expect a good 951 with a good starter and just charged battery to be between 130-150 but more importantly I expect the two cylinders to be within 3-5% of each other.

    You can not really use the gross total compression to judge the health of the engine unless it is very low (say, >100) and has read so with a charged battery, a known good starter, and more than one gauge.

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