1990 550SX All original - Time to freshen it up. First service in 30 years.
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  1. #1
    PWCToday Newbie
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    1990 550SX All original - Time to freshen it up. First service in 30 years.

    I have a box stock 1990 550SX that I'm going through. I have worked on many 2 & 4 stroke dirt bike engines, doing full rebuilds, splitting cases, etc. but this will be the first time on a Jet Ski engine.

    This ski is one of three skis that factory Kawasaki gave to the Baja 1000 winning team of Larry Roeseler, Danny LaPorte and Ted Hunnicutt Jr. It's all original. Never really been serviced that I know of. With that being said, I want to keep it as original as possible but also do some upgrades for performance and some of the standard upgrades that most do. I've done plenty of research on this site and others and am ready to get started.

    The ski only had a few hours on it when I bought it. I don't remember how many seasons I put on it but it ran great for many years. It wouldn't start this season. It seemed like no fuel. Put a carb rebuild kit and still nothing. Brought it home and checked compression. 90 pounds or less in each cylinder. It needs at the least a fresh top end. I would also like to improve the overall performance, maintain reliability and look as original as possible.


    Here's what I'm thinking:


    New pistons & rings
    GroupK 550 "SLEEPER" ENGINE KIT

    Includes cylinder porting, decking, and manifold matching; cylinder head modification;
    cooling system upgrade; carb circuit upgrade; flame arrestor mod; pump nozzle boring
    Disconnect Rev Limiter

    Remove choke, install manual primer
    Ride Plate - On the shelf
    Straight bars & quick steer plate - Done
    New grips (could use suggestions)
    Replace Throttle (could use suggestions)
    Replace Grate (could use suggestions)
    Replace impeller (could use suggestions)
    Replace mat - the stocker is coming apart (could use suggestions)
    Patch & paint nicks & dings
    Polish & wax (or whatever else works, ceramic?)
    New OEM Graphics - Shipping now

    Pipe? I have a Westcoast pipe on the shelf. Group K's says the sleeper kit works with the stock exhaust. Not sure if the pipe will have any advantages. I will sell it if not needed.


    Sorry for the long post. I'm a moto guy and don't know much about Jet Skis other than riding them on and off for decades. Please let me know what are the best mods & parts you would do to build a solid, reliable river cruiser.

  2. #2
    PWCToday Newbie
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    Sent you a PM.

  3. #3
    I dream skis E350's Avatar
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    I am the least knowledgeable person on this forum but I suggest that you put an ounce of Marvin Mystery oil in each of the spark plug holes. Put the spark plugs back in and use a fresh battery with the battery charger hooked up and turn the engine over for a while without the spark plug wires on and see if the rings loosen up and your compression comes up.

    If so, it is still warm in Sacto right now, so ride it and get used to it before you take it apart.
    Learning Slowly...

  4. #4
    PWCToday Newbie
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    Quote Originally Posted by mandm27 View Post
    Sent you a PM.
    Thanks for the info. I really appreciate it.

  5. #5
    PWCToday Newbie
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    I found what looks like a factory blemish under the left side panel. It doesn't look like it was hit as there's no damage anywhere in the area. Anyone seen this before?20201010_163749.jpg20201010_163742.jpg

  6. #6
    PWCToday Newbie
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.


  7. #7
    PWCToday Regular Camaro70's Avatar
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    No expert either but go through the usual problems and if you can’t get it to run or pull better compression your plan sounds like a good one.Cant go wrong with group K and being able to use pump gas and still get major performance upgrade.
    As for the pipe the stock one is good and can be modified to produce just as much as most aftermarket I still enjoy the sound of a WC or Cauffman and lately luckily enough to get my hands on FPP.Also when you pop the hood it’s looks mint.
    89 Kawasaki 650sx-Coffman pipe,west coast waterbox,WC exhaust manifold dual cooled,Mariner head,mikuni Sbn44mm,jetsport intake,k&n arrestor,blowsion 4 degree bars,r&d intake grate,OP ride plate,hydro turf

    83 550/650 WC pipe,supertrapp waterbox,mikuni bn44 WC ready carb,WC intake,WC head,jetinetics arrestor,blowsion 0 degree bars,odi lock one,Mariner ride plate,pjs intake grate,marble hydro turf

    86 550
    92 waverunner 650

  8. #8
    PWCToday Regular Camaro70's Avatar
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    Grips- odi lock on or vintage hydrosport/ame
    Billet trigger throttle lever
    Hydro turf mat molded I prefer over cut or grooved
    Impeller-skat or Silas-you can go variable pitch but depending on the how much power your making group k I believe has a recommendation.also riding style and location has to come into play there as well.so preference is key too.
    Open intake grate first before you introduce a top loader style
    Ride plate again what style riding.are you Freeride or looking to bouy race or all around.I use a deep plate with fins on my 550 with a pjs top loader cause we ride in chop and it hook ups better on the low end.staight 16 pitch with the skat trak impeller.
    Check out the build threads a lot of valuable advice and experience from people who have done this before.
    89 Kawasaki 650sx-Coffman pipe,west coast waterbox,WC exhaust manifold dual cooled,Mariner head,mikuni Sbn44mm,jetsport intake,k&n arrestor,blowsion 4 degree bars,r&d intake grate,OP ride plate,hydro turf

    83 550/650 WC pipe,supertrapp waterbox,mikuni bn44 WC ready carb,WC intake,WC head,jetinetics arrestor,blowsion 0 degree bars,odi lock one,Mariner ride plate,pjs intake grate,marble hydro turf

    86 550
    92 waverunner 650

  9. #9
    PWCToday Newbie
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    Quote Originally Posted by Camaro70 View Post
    Grips- odi lock on or vintage hydrosport/ame
    Billet trigger throttle lever
    Hydro turf mat molded I prefer over cut or grooved
    Impeller-skat or Silas-you can go variable pitch but depending on the how much power your making group k I believe has a recommendation.also riding style and location has to come into play there as well.so preference is key too.
    Open intake grate first before you introduce a top loader style
    Ride plate again what style riding.are you Freeride or looking to bouy race or all around.I use a deep plate with fins on my 550 with a pjs top loader cause we ride in chop and it hook ups better on the low end.staight 16 pitch with the skat trak impeller.
    Check out the build threads a lot of valuable advice and experience from people who have done this before.
    Thanks for the info. This is the kind of feedback I'm looking for. As far as riding style, I'm an old guy that still likes to play around on the river. We have a group of 5-10 guys that have stand ups. The ski stays on the Colorado river between Blythe CA and Parker AZ.

  10. #10
    I dream skis E350's Avatar
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    Jul 2015
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    Sacramento Delta, CA
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    Re: 1990 550SX All original - Time to freshen it up. First service in 30 years.

    Those allen head bolts are not factory.
    Learning Slowly...

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