crank seals, right?
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  1. #1
    I dream skis
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    crank seals, right?

    Picked up a 1995 GTX (657x engine) as a project ski, and it has been a project.

    Previous owner stated it wouldn't do anything other than idle in the water, would bog and die off idle, thought it was a carb issue, didn't know how to rebuild carbs. We compression tested it and found good compression. I noted it had original gray tempo fuel line and also was confident it was a carb issue.

    I got it home and replaced all of the fuel lines, cleaned out and confirmed the fuel selector was not clogged, replaced the o-ring and filter, and then rebuilt the carbs.

    When rebuilding the carbs, I didn't find them terrible, no green goo. I did find a stuck needle and seat, the low speed screw on one carb all the way closed, and one carb filter mostly full of sediment. I verified it had the stock jetting and I reused the stock popoff springs, which were the same length and showed the same resistance (I don't have a tester). I was 100% positive I'd found the issue with replacing the needle and seat, new filters and correctly adjusting out the low speed screw.

    Nope. Same issue only modestly better. Idles great, lean bog off idle, and it will not tune out. Best I can get is with the lows about 2 1/4 out (full turn past stock). There, if the engine is cold it will come off idle slightly flat but otherwise run well through the RPM and throttle range, but after it warms up it only runs well on the high speed jet, if you can get it there.

    Another data point, the boat is run at 7400 feet elevation, so there is no way in hell it should need to have the lows turned way out if everything was ok.

    I've since opened the carbs up two more times. They are clean and nothing is clogged, and I didn't screw up rebuilding them according to the schematics.

    The boat runs the same on the reserve pickup, so that should rule out a pickup problem unless both are broke?

    The fact that high RPM runs fine makes me want to rule out ignition. A good idle with easy starting and good upper RPM operation also make me think rotary valve is timed ok.

    So, that leaves crank seals, right? I took the PTO cover off, it looks clean in there with no oil smutz on that flywheel. I haven't looked at the stator cover. No hydrolocking on oil or anything like that, but on the trailer idling it does seem smokier than I would expect.

    Anything I should rule out before I yank the engine and start really looking for air leaks?

    Thanks...
    1992 750SX with mods
    1991 X-2
    1996 SS

    I have more skis than friends.

  2. #2
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: crank seals, right?

    Better check compression to start , especially at 7400 ft , the no power zone on a good 2 stroke engine , bet it's below 110

  3. #3
    I dream skis
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    Re: crank seals, right?

    Compression is 125 in both, which is what stock boats pull up here.
    1992 750SX with mods
    1991 X-2
    1996 SS

    I have more skis than friends.

  4. #4
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: crank seals, right?

    Testing in water or on a stand for results

  5. #5
    I dream skis
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    Re: crank seals, right?

    Quote Originally Posted by Bionic racing View Post
    Testing in water or on a stand for results
    For a compression test? Dude, it is not compression.

    I've been troubleshooting it both in water and on trailer. The bog is bad enough that it has a flat spot even on the trailer under no load.

    On water, without the low speed way way out it will not come off idle.
    1992 750SX with mods
    1991 X-2
    1996 SS

    I have more skis than friends.

  6. #6
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: crank seals, right?

    Do you want help or not , simple question ?
    If bog is worse with water added , by hose or lake it could be inner head o ring leaking water into combustion chamber causing a bog condition , take to a shop , check all air leaks , pull engine , rings seals gaskets and your done , your welcome
    Last edited by Bionic racing; 07-19-2020 at 10:13 AM.

  7. #7
    Resident Guru
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    Re: crank seals, right?

    When carbs were apart, did you actually run something thru the jets? Or just blow them out with air or cleaner?

    Dried fuel residue will not wash off. Jets dont need but a thin film to cause an obvious lean condition.

    Another common problem with that series motors is rotary valve clearance. The intake manifold gets scraped by rotary valve every time piston is on the down stroke. Very little bit of wear outside of factory clearance will make the engine run poorly.

    There are several tale tale symptoms from your description to not having any power and dying when put in water.

    It can easily be a combination of the two. That makes things more difficult to diagnose correctly.

    I am going to assume you are reinstalling the airbox with stock flame arrestor mesh each time.

    Those 657 motors are extremely reliable and ran well in their day. If ski has not been abused, neglected or someone not knowing what they are doing, will run forever.
    Last edited by Seadoo timebomb; 07-19-2020 at 11:52 PM.

  8. #8
    I dream skis
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    Re: crank seals, right?

    Blew jets out with carb cleaner and compressed air. They show no sign of corrosion or gunk- I also eyeballed them held up to a light to confirm no sign of gunk inside.

    I heard rotary valve clearance issues tend to create poor starting issues. Accurate? This thing starts quickly and idles well in and out of the water.
    1992 750SX with mods
    1991 X-2
    1996 SS

    I have more skis than friends.

  9. #9
    PWCToday.com Is My Home Away From Home kcr357's Avatar
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    Re: crank seals, right?

    Did the carb kits have a new seat oring?
    How many gerbils could a gerbil jammer jam if a gerbil jammer could jam gerbils?


    "You build cheater motor's & still get smoked !!!!"
    "Its not your fault. You just don't understand what you're talking about. "

  10. #10
    I dream skis
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    Re: crank seals, right?

    Quote Originally Posted by kcr357 View Post
    Did the carb kits have a new seat oring?
    I put in a new needle and seat as part of the carb rebuild and would have put an oring on there if the old needle/seat had one.

    If needle and seat were leaking, I'd be troubleshooting a rich condition right? I'm very confident I am dealing with a lean condition off idle.
    1992 750SX with mods
    1991 X-2
    1996 SS

    I have more skis than friends.

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