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  1. #1

    Join Date
    Sep 2013
    Austin, TX

    Rebuilt gp1200r that DIDNT blow up

    Seems like every day I see new posts from guys posting failures after fresh rebuilds on the gprs. That shouldn't be. I have 30 hours since I rebuilt mine this winter and it runs like a champ. I tore mine down to every part nut and bolt though. Didn't cost a lot, but did take a month and a lot of hours. In the end its worth it. Little things go out of sorts I know right away. I know the ski and engine very well, its sound, its ride, its feel. I wouldn't trade my gpr for a brand new ski right now. I'm not an expert. Last September I bought the gpr. My test ride was the first time I'd been on a jet ski. I'll write this up once. This was my rebuild checklist, but it was based on my research here. Some might say i missed some steps, others might think I went overboard. you'd both be right, but this worked for me. Everything I chose here was based on what is already written here, and by talking to a few of the experts that I'm grateful spent quality time educating me.

    background, I had a complete failure. Bought the ski in bad shape for a song, water ingestion, past rebuilts, missing bolts. you all know the drill. It failed beautifully blowing a rod through the crankcase.

    1. pulled the engine... completely.
    2. started with a used crankcase. tapped all holes with WD40 to clean the threads. Cleaned all mating surfaces to bare metal with a straight edge and wd40... carefully.
    3. picked up a very low hours used crankshaft. Yes used. I got it from a pro shop, and it was very clean.
    4. all new OEM crank seals
    5. Cleaned every bolt with a wire brush on my drill press. Clean bolts and clean holes are key. Torque specs are paramount. Cruddy thread mates can cause a bolt to torque too soon. If all the threads are clean, the bolt doing its job at its torque spec.
    6. Assembled crankcase per oside bills writeup
    7. Kept the oil pump. Tested it with a drill. Checked the check valves, all new tygon lines and oeteker clips at joints. left it a little heavy on the hash marks for oil (1/16th inch past marks)
    8. installed new OEM base gaskets.
    9. new rings on the remaining two good jugs.
    10. OEM replated cylinder for the third. Pro-x piston.
    11. reused head gasket but cleaned it completely with acetone to bare metal, then copper coated it.
    12. reused all exhaust gaskets with a little copper coat.
    13. removed chokes and put in a primer.
    14.Rebuilt carbs and installed. Felt bad I had creased some plastic disks in the rebuild. Bought new parts and rebuilt them again just to be sure.
    15. Complete cleaning of powervalves plus added wave eater clips.
    16. New powervalve gaskets
    17. All new tygon fuel lines
    18. removed fuel selector
    19. drilled and jetted returns
    20. Had one set of iffy reeds. I could see light through them. so I replaced them with OEM.
    21. Added an electric bilge pump.
    22. Every bolt was tightened exactly to its torque spec.

    I have a spreadsheet of costs and figure this all cost me ~$1400. I got some great deals from guys here but the message is, even with catastrophic failure, a rebuild doesn't have to break the bank. My ski is basically stock with a stinger pipe and aftermarket grate. It came with both. I ran 61 on gps with a full tank of gas today which is plenty fast for me. The stock intake and carb setup works fine and is proven.

    There you have it. A recepie for a gpr rebuild that has worked 100% of the time for me . Quit abusing these old gprs or sell them to me and I'll build a fleet.

  2. #2
    Sounds awsome man mine blew up again in the first build seems like the ring failed on the piston

  3. #3
    Almost's Avatar
    Join Date
    May 2010
    Cape May, NJ
    Nice job, you should be able to find some more speed in it. Look at what I'm running in my sig.

  4. #4
    cmgww's Avatar
    Join Date
    Jun 2010
    Indianapolis, IN
    That's the thing with 2 strokes. Stock, if taken care of (Yamahas), they run forever. Modded, they need more attention and are prone to failure if tweaked too much. Upside? Relatively cheap to rebuild vs the 4 strokes. Also, cheaper to modify. Downside, what I they are worse on oil and gas.

  5. #5
    How did you make sure your rings were positioned perfect when putting the jugs on? Im on this step and have 2 of the three on. But am questioning it. They went on smooth and move smooth. How do i know the ring isnt preloaded on the locating pin? I read you slightly turn the cylinder back a forth but i cant tell by feel.Would the jug go on if they were not on the pin perfectly?

  6. #6

    Join Date
    Sep 2013
    Austin, TX
    Others have had more experience with the pin issue than I, but I first made sure each piston had a good pin securely in place. Then I positioned the rings in the grove around the pin. Then by hand I pressed the ring in put the assembly in the base of the jug. The prongs on the base of the jug offer a nice way to see how the ring sits in the grove after compressed. When the ring looked properly around the locator pin, I seated the jug down on the crankcase. I think the issues come when the piston doesn't have a good pin. Pin comes loose, rings spin, and bad things happen. I was happy with the pin setup in the pro-x piston and my remaining two stock pistons seem to have good pins in as well.
    cmgww said it right. I also like that the old GRP hull is built like a tank. All these new hulls flaking and cracking scare me. My docking ramp is surrounded by concrete. Docking a few weeks ago my sister swears she saw a snake, panicked and gunned it into the wall. bounced off like a bumper boat.

  7. #7
    OzarkYamMonster's Avatar
    Join Date
    Oct 2012
    Lake Of The Ozarks
    1st things 1st ... I assume your sister did not get her. I however was not lucky enough to "just bounce" I T-Boned a kawai 300x , cracked up my upper hull (bow) pretty bad & put some major cracks in the the lower hull (bow). But the repairs were pretty simple & never have had an if with it. My friend Spark, took a hit & punch a big hole in it. Kind of like my old Saturn and he has to get a new hull. LOL I agree , that every time you mod this suckers they start to push on the great reliability that Yamaha's are known for. Keep tour Yammy 2 stroke ... nothing quite like it

  8. #8
    TX21's Avatar
    Join Date
    May 2007
    North Texas
    I got about 40 hours on mine and the only issue I have had was the easy stuff like pump shoe, ride plate bolts, etc. Built my motor too with WSM platinum pistons, crankworks crank, still running strong.
    My fuel did gel up over one winter and cost me carb clean and a lot of diag. Even pulled the motor thinking I had an air leak. Other then that I don't want another sit down of any kind. They cost a lot more and don't really pay for me to get one.

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