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  1. #1
    ford man's Avatar
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    hi new here (compression readings)

    hi everyone, i am new to this forum,i was just wanting some advice i have a 2000 seadoo GS (718cc) 2 stroke. ive owned it for four years and ive never had a bit of trouble out of it until this year. earlier this summer i was having to run it on "reserve" to make it go full speed for it would only idle on "on" postion(fuel selector switch)
    i have yet to do it but plan on overhauling the fuel system ( ive never touched carbs i will rebuild them for starters,replace selector switch,sediment bowl, and old grey fuel lines) i had it out about a month ago was running fine the first day and the secound day as well until it started cutting out and eventually died. and restarted repeat. so i got it home to blow water out of it and it wouldnt start nor turn over i charged battery and got it to turn over but wouldnt start. so i then took the plugs out and spun the PTO(by hand and it spun just fine so it know its not siezed up) i got it started (on trailer runs fine) but itl only start when it wants to other times just sounds like its not getting fuel.(im pretty sure its had a slight lean condition but still cranks fine and nothing comes out of the plug holes) havent lake tested it was goin to wait until i can replace fuel system. i did however, take compression checks and came out with a dead 115 psi in both cyliners(note this is the first time ive ever taken readings and has always ran great) i know its low but could dirty carbs or fuel system have something to do with the low readings? i did take it a few times and once got 115 in rear and 125 in front cylinder. ive also heard if their within 10% of eachother then thats good. but is it really important to have higher #s even though they match? if so would just a new top end do the trick?
    ive owned this machine for 4 yrs but have never done anyrhing besides winterizations,change plugs and batteries so im new to working on them please bare with me.
    any advice would be great thanks -cody


  2. #2
    wotxxxsd's Avatar
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    All compression guages give different readings and the fact that they are very close tells me its probably your Carbs.
    It's good to rebuild them every season so your doing great for not doing it for over 4+ years.

  3. #3
    ford man's Avatar
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    alright i appreciate it ive been told it HAS to blow 135-150psi so good to know im just thinkful their close readings. like i said its been a great ski never an issue. only 85hp but itl his 60 mph on a good day. so ill plan to do fuel system rebuild and carb rebuild
    thanks cody

  4. #4
    Joe Stang's Avatar
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    Clean the carbs and change the fuel lines. Run her for the rest of the season then get into the engine this winter. You'll be fine.

  5. #5
    wotxxxsd's Avatar
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  6. #6
    ford man's Avatar
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    hi guys, thanks i appreciate the advice looks like theirs still some hope left in the ski without having to rebuild the motor. i already like this forum alot better than (seadooforum.com) that one was okay but they have some rude people that think they know everytjing about working on a seadoo. CT watercrafts, would you recommend a new top end? or just keep running it? the motors cranking as it always has. and its always kinda been a little hard to start if its not warmed up what could this be? ignition or starting system you think? and since its always been hard to crank and start( like soemtimes i have to push the start button 2 or 3 times for it to crank could this cause the low # of compression?)
    -thanks cody

  7. #7
    Joe Stang's Avatar
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    Like I said. Clean out the carbs, replace te fuel lines. And run the ole girl for the rest of the season. Then worry about the top end freshening during the off season. I've seen skis come in with 95psi on each cylinder running perfect they were at 95 because it had 450 hours on it. Was just worn and needed a freshening up. Fix the fuel side, richer up the oil pump a tad and have at it!

    If you have are having it click and the starter is hard starting you most likely have a weak starter as well.

  8. #8
    ford man's Avatar
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    alright thanks and thanks for the quick response. the guys at the seadoo forums said my motor was trash because of the low #s glad to have more better quality advice on this topic. ill do just that.(ive also heard with a new top end the bottom end isnt going to last long at all? is this true?) thats what the other guys said i think they were kinda shady mechanics though.

  9. #9
    rhyne717xp's Avatar
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    My 717xp runs about 130/135 psi. Sometimes i can get 135/140, mine has been this way since i started doing compression tests. I think my engine had a top end job, im thinking who ever did the work used a thick cylinder base gasket.

    My mom had some shady tree mechanic do some work on it several years ago as a birthday present. He said he did a top end "scary". I didn't know much about seadoos then. What i did find out is I about sank it because of his hillbilly engineering first trip out. He used rtv as a gasket between manifold and head pipe. It took on hella water. I started doing my own wrenching from then on...

    The engine has maintained compression in the 130's. I may at least hone and rering mine this winter and set the proper squish gap ti get 150 in each hole. Until then just ride it!!!

  10. #10
    ford man's Avatar
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    man, that sucks good thing you were able to recover it!! alright sounds good thanks for the advice like i said its been a great bike and ive never done compression testing on it until now therefore its probably been running 115 psi this whole time(4yrs) and never given me any trouble. i see you have 717cc i believe 717-720cc are considered the same motors. ( their like banchees on the water) good reliable quick manoverable motors i can push about 60 with mine on good calm water very fun motor

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