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  1. #1
    ford man's Avatar
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    hi, new here(what can increase compression?)

    i am new here . i am just wanting advice i have a 2000 seadoo gs 718cc 2 stroke and my compression readings are 115 in both cylinders. i know their low i was jw if perhaps there is anything i can do to ti besides a top end or motor rebuild to increase compression. im new at workin on these so please bare with me (i dont think it matters but im using a 0-300 psi gauge that i am renting from a parts store(autozone)
    thanks cody
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  2. #2
    wotxxxsd's Avatar
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    All guages read different #'s.
    Atleast your cylinders are equal.

    Does it crank and run?

  3. #3
    ford man's Avatar
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    yes, however ive had a slight lean condition. but will start and run on trailer havent lake tested it because i plan on rebuilding carbs, new selector switch,and fuel lines ( i have grey lines)
    - cody

  4. #4
    wotxxxsd's Avatar
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    Welcome aboard the hulk.

    Run it in the lake after the Carbs are rebuilt.
    You might be able to get another season out of the motor before rebuild.
    Even compression is a good 1 st step.

  5. #5
    ford man's Avatar
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    okay thanks. would a fresh top end do the trick instead of rebuilding the motor or? also how much do you think a motor rebuild or a top end would cost if i took ti in to be done?
    Last edited by ford man; 07-23-2013 at 10:55 PM.

  6. #6
    ford man's Avatar
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    ill also add that i took these compression readings the other day but went out today to do another check of them and the i got one beep after hitting the starter (dead battery could the battery have possibly been low when taking the readings? if so how much would it affect the outcome of the compression and how long should i charge the battery before running another compression test?

  7. #7

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    you do need a good battery when doing the compression check. if the ski starts and runs, if the cylinders are even, rip on it. it might give you a better reading when the engine is warm. run it in the lake 15-20 minutes, then test compression.. might give you better confidence..

    i ran a 951 all summer last year on 120 in each cylinder. and it ripped. was not a hole shot monster, especially with me on it, 240lbs, but it would fly on the upper end, and had lots of top end power. the fialure i had wasnt related to compression at all, so if i didnt have the failure i had, i would have rode it this year as well, until i just melted a hole or what not.

    I am of the school, that if your gonna get into a motor, you need to do it "right" , which at the very least includes going through the bottom end for cleaning and inspection. I dont think i would mind throwing a top end on a motor if it had 50 or less hours, as long as i knew that there were no debris, ring parts, or metal shavings down in the bottom end.

    i really think the cheapest route, is something like an sbt rebuild. ive read good and bad things about them, but still, for a warrantied motor, cant go too wrong there.
    but again, im of the school, if your gonna do it, do it right, so i tend to get out the wallet, and go for the best that i can for my buck and that includes good components, and rebuild by reputable shop.

  8. #8

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    in other words.. its already middle-late summer.. rebuild the carbs, get it tuned, and rip the hell out of it. if it blows, meh, whats the harm? you have a winter project either way.

  9. #9
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    I'm betting that gauge is not very accurate. Also a low battery and slow cranking will give lower compression numbers. Clean the fuel system and run it.

  10. #10
    ford man's Avatar
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    Myself, i believe you were correct i rented another compression gauge from another local parts store and here are the results. (i also quick charged my battery for 30 mins before doing this test) i think their good #s so now ill move onto the carb&fuel system rebuild then go play
    -cody
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