Yamaha SJ 1200cc Conversion.
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  1. #1
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    Yamaha SJ 1200cc Conversion.

    In response to all the private messages I have received over the years I am thinking of starting a thread on how I build my SJ 1200cc conversions. Since I have built 4 of these, I believe the best build would be the first one because it was the most economical and mainly used stock SJ parts and and Wave Raider part. I have limited amount of pictures because at the time I did not think anyone would be interested. This is a very fun recreational ski to ride. All stock, handles great, turns awesome, linear power with great bottom end. 58 to 60 mph. depending on set up and impeller. 155 psi compression pump gas. I do have to thank my daughter she was a big help on this project.

    Purchase a 2008 or newer Yamaha SJ hull.

    We purchased a 1996 1100cc Wave Raider for ($500.00). if possible find one running and complete because we will use a lot of parts from it.

    You can also purchase a 1200cc GP. This will make the project a little easier but we had a hard time finding one for under $1000.00 close to where we live.

    Parts we used from SJ:
    Hull, hood handle pole.
    SJ gas tank or fx1 gas tank. Recommend fx1 tank.
    fuel pick-up
    battery box
    gas fill tube
    foam in front
    throttle cable
    start stop switch
    stock wiring harness from electrical box.
    mid-shaft housing
    steering cable
    stock exhaust tube


    Wave Raider parts:
    Complete engine with electrical box mounted on motor.
    exhaust pipe
    exhaust rubber tube
    stock water box parts
    engine cradle system.
    rubber bottom bumper
    engine mounts
    mid-shaft
    155 complete pump with steering nozzle.
    coupler cover


    After market parts:

    impeller
    ride plate
    intake great
    ADA couplers
    Jet Dynamics 155 pump shoe
    Wave Blaster drive shaft
    additional SJ exhaust tube.
    (2) 2 1/2 inch 90 deg. rubber radiator hoses. Truck part from International School Bus.

    Parts you have to make: I do have pictures that I can post later.

    Water box with dual exits.
    battery mounting box plate
    cradle modification
    drive shaft modification

    If there is any interest in this the next post I will post some pictures and start with engine location, cradle, engine mounts.

    Thanks
    John
    Blockhead Racing
    Blockhead Racing Team

  2. #2
    PWCToday.com Is My Home Away From Home Yamabooeey's Avatar
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    Re: Yamaha SJ 1200cc Conversion.

    Why the dual exhaust? More power than the single exhaust? Noticeable?
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  3. #3
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    Re: Yamaha SJ 1200cc Conversion.

    Good question! We did test on both. When we began to add more horse power to the motor, on the dual when we would close off one side we would loose some max RPM. This was with the stock tube diameter exit. If you do a single exit I would increase the diameter. If you use the 1200 gp ignition box single exit on the left side of the ski would work and allow room to mount the box close to stock SJ position. It was all fun! Dual exits sounded good and looked cool. It also gave me the ability to restrict one side as desired, or run wide open. I also like the exit tube running up hill to prevent water from running in while floating. Same location as stock but on the opposite side of ski. The volume of both exits is close to the same volume as the stock Wave Raider exit. The ski is loud!
    Blockhead Racing Team

  4. #4

    Re: Yamaha SJ 1200cc Conversion.

    Would luv to compare ski builds w my sj1200. We tried to stop by and say hi to u guys last yr at wfs but u must hav been having a bad day. Lol
    Man - Dude - Buddy

    TeamBustOutBMX

  5. #5
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    Re: Yamaha SJ 1200cc Conversion.

    Hey now. We never have a bad day in Havasu.
    Blockhead Racing Team

  6. #6
    PWCToday.com Is My Home Away From Home tshank123's Avatar
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    Re: Yamaha SJ 1200cc Conversion.

    Wondering why you listed the rubber bottom bumper. Is that required to dampen vibration or something? I know for sure it wouldn't fit without cutting it down.
    High Speed Industries - http://highspeedind.com/

  7. #7
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    Re: Yamaha SJ 1200cc Conversion.

    Engine Location.

    This installation requires using the JS engine mount hard points.
    Remove SJ midshaft and housing. Replace it with the Raider midshaft and housing. Remove coupler. You will notice the Raider splines on the inside of the shaft are closer to the engine. On the SJ the spline are more towards the back of the ski. This spline difference will allow for a Wave blaster drive shaft to work with the Raider pump.
    Remove SJ engine mounts and replace with Raider mounts. I like the idea of the Raider mounts being heavier duty.
    Bolt cradle to Raider cases and take to your local welder and weld (2) aluminum bars 3" x1/2" as shown in pictures.
    Next put crankshaft in cases with Raider coupler on crank shaft and place engine in ski on mounts. Measure the distance desired for your engine location. Cut mid shaft coupler to desired length in miter box and take to local machine shop to tap new threads. We liked the engine to be balanced equal distance between JS mount locations.
    The engine location will also be to high. We fixed this problem by grinding off the bottom of the Raider engine mounts. (shown in picture). If you take your time with this you can get the engine to align perfect with no shims.
    Shave rubber damper to desired height and glue to cradle, if you bolt it in place the bolts can hit bottom of hull. We tried not using the damper and in a surf race we broke an engine mount and cradle. Once we started using it we never had a problem again.

    John
    Attached Images Attached Images
    Blockhead Racing Team

  8. #8
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    Re: Yamaha SJ 1200cc Conversion.

    Sorry forgot.
    Once engine aligned, drill new holes in cradle and bolt in place. Right front bolt needs to be shorter then stock to fit under intake manifold. We slotted rear holes for studs for easier access. shown in picture.
    Blockhead Racing Team

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