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  1. #1

    97 GP1200 coming back to life

    Hello everyone,

    I have decided to bring my 97 GP1200 back to life. Let me give you a bit of history on this ski. I got this Ski back in 2001, and its been a solid jetski for all these years. Back in 2002 the bottom of the hull cracked and water came in to the point that the engine was almost under water. I was able to get the water out and ride it to the marina. Nothing happened to the engine or anything mechanical. I fixed the hull to the best of my abilities at that time and to the water it went again. Then in 2004 I got my self a 2001 LS2000 jeatboat, and the jetski was put away for a whole bunch of years. I would turn it on every once in a while and rode it like once or twice a year if anything. Last year i took it out with a couple of friends to jump some waves and the hull cracked again. This time i just left it there and i did not fix it. About a month ago my LS2000 got a PTO piston failure and I decided to borrow the engine from the GP for the LS since it is what i use the most. Then I started to take a look at the damage in the hull and the condition of the ski and decided that I want my jetski back. So I am going to try to restore it to what I would like the ski to look like. I got a new crank and a new cylinder case on ebay and i am in the process of grilling the sleeves. i need to get a standar piston and new rings.

    This brings me to a couple of new questions:
    1) I have 3 sleeves that are standar size and for wich I have only 2 pistons that match. Can I just buy a 3rd piston and drop it in or do i have to hone it? The sleeves were alrady honned and they were on an engine that was working.

    2) They tell me that is a good idea to change the rings on this engines at least every 200 hours. Can someone tell e a bit more about that? Is it true? False? Do I have to do anything special to do that? Hone? bore? etc? Also can I buy just any ring set that is for the size of piston that I have and drop it in or do they have to match?

    3) I had some damage done to the bottom crack case and i am not sure if it can be reuse. I have a feeling that it can but I need your help. Can someone take a look and let me know?

    Well now its time for some pics so let me see if i can get them to work.

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  2. #2
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    The right way to do it is to measure the piston and cylinder. Then hone the cylinder until the piston to cylinder clearance is correct. There is a little bit of fudge room with the clearance but the more perfect you get it, the longer the engine will last. And the rings will seal better. Since you are putting a used top end together, things are already worn in and you probably can't hone it to the perfect clearance. so at least measure the clearance and if its too huge, you'll have to overbore it to the next size up.

    Rings every 200 hours...not a bad idea, but not necessarily the best idea either. First of all, alot of these engines don't make it to 200 hours. Things happen...oil lines, plugged carbs, overheating. But with great upkeep and some luck you'll get to 200 hours and beyond. If the compression is still good, there wouldn't be any need for new rings. Plus new rings on old glazed cylinders probably won't seat/break in properly.

    Crankcase looks usable. Its kinda hard to judge by the pics though. Clean up any damage. As long as there isn't any holes or damage to the sealing surface you should be ok. Pressure test the engine for leaks once you get it back together.

  3. #3
    Thank you Cutlass for your answer. I am making a list of everything that I have to do and change, so that I wont forget and so that i can get as much help as I can.
    Here we go:
    Buy complete gasket kit
    Buy new standar piston
    Buy and install both trim cables
    Buy and install new starter
    Buy new display
    Check clearance in the cyl case and bore if necesary. (if needed buy 3 new pistons to match bore)
    Assamble the engine with all the new parts and gaskets and do a leak test
    Finish fiberglassing the hull. Inside and outside.
    Paint the bottom of the hull.
    Custom paint the hull
    Install the engine and align with impeller shaft.
    Remove old Gas and fill up with new gas
    That is all that comes to mind right now. I am sure I will be adding more later
    Here are some more pictures:
    The new cover in the seat
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    The fiberglass repair inside
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    The fiberglass repair outside
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    The new parts for the engine
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  4. #4
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    Add rebuild/clean the carbs to that list. Especially if they've been sitting a while with old nasty gas in them. Only use genuine Mikuni rebuild kits. The aftermarket kits just don't work.
    If you buy the OEM Yamaha complete engine gasket kit, its missing 3 gaskets. It doesn't come with the 3 gaskets between each carb and the carb mounting plate. Its #43 in the microfiche. So order those too if you need them.
    Planing on doing any mods? Flame arrestors, primer kit, Carburetor Drilled Return Pressure Balancing Mod?

  5. #5
    Thank you for the advice Cutlass. I will be adding that to the list. I will be doing the flame arrestors. I have a friend that gave me his from his old GP. And I will add that to the list too. Primer kit sound like a good upgrade since I remember that the ski was a pain to start. Can you tell me a bit more about the other mod? The Carburetor Drilled Return Pressure Balancing Mod. What is it intended for? Also one I get everything up and running I will provably start to do a lot more stuff.

  6. #6
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    The Carburetor Drilled Return Pressure Balancing Mod is a reliability mod. Read all about it in this thread -

    Also since you're doing adding flame arrestors you'll need to change the carb setting to get the thing to run correctly. Luckily its already all been figured out by others here.
    I have Riva cone flame arrestors, choke plates removed (primer installed) and it has stock compression and stock ports.
    My carbs are set up like this: 135 main jets, 100 pilot jets, Low speed screws out 1 1/4 turns, High speed screws out 1 1/2 turns. 1.5 N/S with 115 gram spring. All three carbs are set up exactly the same. Runs perfect.

    So you'll need
    3 x 1.5 needle/seats
    2 x 100 pilot jets (one carb should already has a 100 in it)
    3 x 115 gram springs (but those should be in the Mikuni rebuild kits, so you won't need to order those separately)

  7. #7
    Ok here is an update of what is going on with the build. I did not wanted to order the parts until i knew that I was going to be able to take out the sleeve out of the Cylinder case. Today I was able to do it. This is how i did it incase someone has the same problem:
    After grilling it for about 30 minutes at 375 in the oven I noticed that I was able to rotate the sleeve enough to one side that they sleeve wall between the wholes of the sleeve would fall in the holes of the Cylinder case. Then I got a dremel tool with a cutting disk and started cutting. I recomend to use a slow speed and a to go slow. There are to of the seleeve wall that are to thick to cut in one pass so i had to grill them again and turn rotate the sleeve to the opposite side to finish cutting. After that I grilled them one more time and the botom part came out from the bottom and the top part from the top. Here are some pictures of how it looks after is out and cut.

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    So now I am putting the sleeves in the freezer until tomorrow and then they are going back in to the Cyl assambly. I am ordering a new piston Standar size and the gaskets that I need to finish the rebuild of this engine.

  8. #8
    Also I have a question regarding fiberglass. If you see the pictures that I posted here you will see that its all green on the inside and on the outside. I went out to see it now and I see that all the fiberglass is like a brown color. is that normal? Or is that a sign that the fiberglass was no good? I feel really solid when you touch it or knock on it.

  9. #9

    Join Date
    Sep 2008
    Clarksburg, WV

    97 GP1200 coming back to life

    Not sure on the glass issue but I have always had it cure brownish.

    Also, I have a like new front and rear red seat The vinyl is in very good condition. If your interested let me know.

  10. #10
    Thank you akjose. I will let you know if I need it. I am in the process of painting the helm. I put 2 coats of primer and I am ready to start painting it today. I am hopping for a good day so that I can let it cook in the sun for a good couple of hours. Then clear it and polish it. The engine is in the back burner because I am debating on wether to buy a platinum WSN piston or for $20 more go with an OEM. Now I have a new question..... Can you mix and match pistons? I know that 2 of the pistons that I have are yamaha OEM. Now I need to get a new piston. can I just get any brand or do i need to stay with yamaha?

    Thank you again

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