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  1. #1
    Superman! fivespeedsteed's Avatar
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    my rebuild thread.

    i know there are allot out there right now, but i want the best advice i can get.

    my ski dumped number 2 today. its down to 40psi. its getting oil. when i bought it with 95 hours on it, it had only been in fresh water. i put it in salt twice so i think that the rings didnt like that. when i rebuild it i defiantly want it to run salt and fresh water.

    anyways im new to this jetski thing, i bought a running one in good shape for 4 grand hoping i wouldn't have to do this for a while, but here i am. heres what i know about rebuilds:

    most people recommend sending the crank out and getting it trued and welded if its got over 100 hours on it. since im at 108 i was planning on doing this. is it okay to reuse my rods? who do i send it to and whats a ballpark on cost for having this done?

    everyone says use oem yamaha stuff

    so i guess my plan is send out the crank and get it welded and trued (unless you think its not necessary)

    then i was planning on not touching the jugs. is this okay?

    then i was planning on getting oem yamaha pistons and rings and gaskets.

    that it?

    the sbc rebuild kit is appealing but i hear the quality of their motors isn't that great, so how are there rebuild kits? is it necessary to use oem yamaha stuff and true and weld the crank? or should i just buy the 400 dollar rebuild kit, and call it good?

    ski is used on a freshwater river mostly but i like taking it to other rivers and riding it in salt every now and then. id like to be able to do whatever with it, maybe take it to the bug.

    so what should my plan of attack be?

    sbt rebuild kit and nothing else or true and weld crank, oem yamaha stuff. i plan on owning the ski for a while.

    also oside bill does carbs for 85 a piece too right? i should invest in that too correct?

    is it bad for me and my dad to ride this thing together, hes about 200 im 160 ish?

    anything else im missing?

    thanks for your help everyone.


  2. #2
    Superman! fivespeedsteed's Avatar
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    is the difference between a 1200 and 1300 in the jugs or the head? how much can i get a 1300 top end for?

    whats a random estimate on going to a 1390?

  3. #3
    "just sayin".. jetdave56's Avatar
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    I'll let the tuners answer your engine rebuild Qs, but I can tell you that its way too much wt. for that ski,specs. are max 353lbs, even if your dad was lighter, this ski would have the pump pushdown you would get a sluggish hook up.A GPR is designed to be a one person race ski even though it can carry two passengers, it just won't handle well.Now if that passenger is about 100lbs and curvey then that is acceptable

  4. #4
    Superman! fivespeedsteed's Avatar
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    yeah i was figuring that too.

  5. #5
    Superman! fivespeedsteed's Avatar
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    no one has any advice? im calling wfo tomorrow to get prices on boring.

    i did this today in about 2 hours.





    cyl 1 looks good:



    this is cyl 2. the one that has 40 psi. :





    see how the piston on the left edge of it is bent up kinda? i think thats where the ring blew. it looks like its just the pison though. whats the easiest way to spin the motor a little but without kicking the starter so i can see the rest of the cyl wall. im really curious to see what the wall looks like if its bad ill have to port right?

    and 3:



    then this is the underside of the head:



    see the middle piston has all that junk on it, im guessing thats little pieces of my ring.

    then the top looks fine:



    and the carbs before i rip them apart



    so i need to know if i should send out my crank and get it welded/trued and get the jugs cleaned up or bored and if i should use oem yamaha stuff or just go with an sbc rebuild kit.

    also, to pull the jugs, do i have to dissasemble the powervalves or just separate the couplers so i can pull them? and i know the header has to come off. i can do the rings and pistons with the crank case in the ski right.


    right now im looking at sending the carbs to oside bill to get freshened up i guess

    and im going to switch to premix with the island racing kit

    and get an sbc top end kit if no one has any objections. unless wfos porting can be afforded.

    opinions? ideas?

  6. #6
    icky002's Avatar
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    you can try and turn the motor by hand. Remove the plastic cover over the midshaft coupler and give the driveshaft a turn. Remove the spark plugs first.

    Going through the carbs is a good idea.

    You need to find out what went wrong before you rebuild or it will probably happen again.

    Unless your crank is damaged, I wouldn't touch it, at least not until the off season.

    You can't bore these cylinder (nickel silicone coated) so you need to either get a new cylinder, get your old one replated, or re-sleeve all of your cylinders. Post pictures of damage to cylinder/s.

    You can replace the one damage piston or all three. Obviously the one you need to replace go with OEM, but Prox is great too. I have also used WSN platinum which is cheaper with good success so far.

    Bottom line. Before you go nuts post compete pics of damage, get a better idea of what happened to cause this. And I don't see what riding in salt water has to do with the piston rings???

  7. #7
    Superman! fivespeedsteed's Avatar
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    i dont either it just doesent make sense that i beat it up pretty good in fresh then i put it in salt and then fresh then in brackish water and then it let go so just separate the pv couplers to pull the jugs out?

    so if i go with pro x do they come with rings? they have 4 80 mm pistons. piston size 79.90, 79.91,79.92,79.93. what size am i looking for ?

    if all i need is pistons, rings and the head gaskets then i might as well put full on weisecos in there.

    i really dont think my crank is that bad off. id really rather spend money on a good set of weisecos and gaskets rather than send out the crank and all that.

    anyone know about how much sending out a crank runs typically?

  8. #8
    Superman! fivespeedsteed's Avatar
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    riva racing says i should clean the cyl. walls with muriatic acid. this a good idea?

  9. #9
    Superman! fivespeedsteed's Avatar
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    my cyl walls.

    all 3. middle looks more dry to me. probably cant see it in the pic though



    cyl 1 and 2. 2 is the one that lost compression



    this is cyl 2 where the piston messed up.



    it feels smooth to me, im going to clean it real well and see where to go next.

  10. #10
    Nothing like getting air, while sitting in a chair VonnerNIX's Avatar
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    I am in the same position as you are in, except I have a 97 GP1200. Your failed piston and wall look a lot better than mine tough. I think I am going to take my cylinders to get the middle cylinder bored and order an oversized piston to replace the one that failed.

    I am wondering the same thing about the crank as well. I am going to give it a good cleaning tonight and try and check some tolerances, etc.

    As far as turning the crank without using the starter, you should be able to turn it by hand as icky002 suggested.

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