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  1. #1

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    2004 Kawasaki STX 1200 - How to improve performance?

    I just bought a 2004 Kawasaki STX 1200, I think it is called F12 as well. It is a 4 stroke PWC. Anyways, I was reading on the internet that this wc goes up to 60 mph, mine on a mirror like water goes up to 51 mph. I read also that changing some parts it could go as fast as 70 miles. What parts can I get to make this jet ski go faster and react faster, I kinda like it and I don't mind spending up to $1000 to make it better. Some of my friends talk about a supercharge others about adding a turbo, but those are just comments, they don't really know about pwc's... neither do I. I would like to get some logical information on how to improve this wc. Please can you provide me with some honest advice? Thank you, I really appreciate it.


  2. #2
    1200 stx-r's Avatar
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    welcome to the hulk. congrats on the ski purchase. try using the search option, lots of really good info in there. you can start with a different impeller, ride plate, plugs. are you looking to do just bolt on mods or do you want to do engine work as well?

  3. #3

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    I would like to buy performance parts if possible only. I'm in the San Francisco Bay Area and I'm not familiar if someone can do a professional work on a PWC engine.

  4. #4
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    hello gpollacchi, Welcome to the forum. I would start with a R&D ride plate, pump wedge, impeller and a air filter kit.

  5. #5
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Do not buy the grate, it will slow you down by 2mph or more, shreadmaster rideplate is supposed to be good for 4mph, exhaust is more or less free, look at my how to. As far as going really fast on a 12f its not exactly practical, you are 35 hp down from the 15f stock. That is not to say you cant go fast, the motor in your ski is the same bore and stroke as a zx12r, so you could buy low compression zx pistons and add boost or add compression and bore the cylinders to 86mm and build a 1287 and make around 160 or if you swap valvetrain and cams maybe even 200. All of this is not cheap, the pistons alone are more than 600 plus you would need to tune it. You can go about 62 or so if you are willing to really work with the parts you have, make everything flush, reduce drag, pump work, and a few other mods.

    I love my 12, so much that I bought a 15 to build up.

    Sean

  6. #6

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    Hi Sean,

    Thanks for the info. I don't think that I want to have an engine work done, but I'm willing to buy performance parts. So far it goes up to 50mph today. If I get at least 55 or 58 mph I would be happy. What parts and brand should I buy to get the F12 to get close to 58mph?

    Again, Thanks. Guil.

  7. #7
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    First of all the speedo on the ski is garbage, it reads what it wants to, to really know how you are doing you will need a gps unit. Second you will need a more accurate tachometer, I have a tiny tach ~40 dollars. Third I would recommend you read jtskir15's build thread in the project section, do what he did with one exception, keep the stock intake grate and remove the center bar from it, this will let you pick up nearly 1.5 mph if you really work on it, sharpen the other 2 bars and make sure it fits perfectly flush to the pump shoe. You are more than welcome to read my threads in the build areas as well but a lot of it will not apply to a stock ski. Once I finish this 15f I will hopefully be able to get my hands on a 12f to tear up and build to see what can really be done to these skis.

    Best of luck and shoot me a pm if you need anything,

    Sean

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