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  1. #1
    madtown_chris's Avatar
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    stx-15f big bore

    Is there any information out there on a kit of some type to do a big bore on these motors...I sent a few inquiries to a couple different folks...just wondering what punching this motor to say 1600cc's would do for performance. I know macc racing as a supercharged application on top of a 1600cc big bore but I'm thinking to keep this machine N/A and maybe throw a piston in there that ups the compression just a tick...

    The same cams just be able to be utilized...a nice port job of the head would only add performance to this project...while its apart an extrude honed intake/exhaust manifold would get you a few extra ponies as well...

    just thinking what all this woud do to the ski with all the normal bolt-ons...

    thoughts/comments...?


  2. #2
    AaronC's Avatar
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    I've thought about a lot of this stuff too. It all sounds great on paper but you need to tune the motor to what's done. Otherwise it'll never see it's full potential. You can't leave one stone unturned on a project like this, otherwise it turns into a mess. You won't get much info here because the cost to performance ratio just isn't there. Most will jump up to the boosted ski's to go faster. I hear Tim Judge has a package with cams, pistons and ecu that runs strong but I have no idea how much $$$ were talking.

  3. #3
    madtown_chris's Avatar
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    emailed a few sites so I'll see what they have to say for reasons
    Last edited by madtown_chris; 01-28-2008 at 03:23 PM.

  4. #4
    madtown_chris's Avatar
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    yeah the performance/cost must be the big factor, otherwise we would see kits available, so thats the only thing I can think of...I was just curious why there's no info about it or any information to be had...

    it would just be interesting to see what a 1600cc with say 11.5:1 compression would run vs stock

    it seems most of the engine sites I come across stop at modding the 4 stroke engine, so it leads me to believe that the cost would just be too high to mess with internals for the performance gains one would see...

    are the cams on the 15f different than the 250x.....?????

    just a thought while the ski sits garaged as the snow continues to fall...
    Last edited by madtown_chris; 01-28-2008 at 03:25 PM.

  5. #5
    njrealtor55's Avatar
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    since my 15f is getting rebuilt i have been thinking about this for a NA kit.....

    bore cylinder and insert steel sleeves
    big bore pistons
    r&d powershot fuel tuner
    o2 sensor
    cold air intake (rear bucket)
    solas 14/21
    riva free flow


    more displacement, more air, more fuel. the object would be to keep the same rpm, just add more power behind that rpm to turn a bigger impeller.

    the only catch is getting the o2 sensor installed to verify the r&d powershot is set correctly.

    tuned correctly i bet it would put the 15f over 70mph on pump gas.

    comments?

  6. #6
    jtskir15f's Avatar
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    you would have to put the 02 sensor at the very end of the collector because the whole exhaust manifold and collector is water jacketed, even then it'd still be hard to get it right and not screw something up.

    i think you'd need a steeper pitch that a 14/21 since people are already running that with the rpm kit.

  7. #7
    madtown_chris's Avatar
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    ...or an upgraded pump all together...

    ...155mm/160mm

    not sure what more the stocker 148mm can handle

    we're running similar speeds to stock 250's after we're modded that is and they're using the 155mm pump so I wonder now if any N/A 15f's have ever upgraded pumps and to what effect it had on the craft

  8. #8
    Fat Man, Little Boat Region8Ultra250X's Avatar
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    riva;'s 15F endurance kit comes with the 155mm magnum pump i assume you could use the stocker but you would shorten the life span of it considerably

  9. #9
    jtskir15f's Avatar
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    rogue says the stocker is only good to 72 mph then they had some veins break off at speeds higer than that

  10. #10
    njrealtor55's Avatar
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    i will have to agree to that - my brother in laws busted 2 veins when he was running it with his turbo setup.

    i think the pump is def. the deciding factor when building a performance kit for the 15f. will a 250x pump fit?

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