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  1. #1
    Chrisrokc's Avatar
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    Head information

    I am looking to mod a stock 1300 head to go on my ski to go along with all the other goodies I am buying and planning on. Don't want ANY down time over the summer lol.

    Who does this? And how much usually? Also with kind of psi compression numbers are safe and reliable. The shop I have been taking my 1300r to was telling me that for longevity I really would want to steer clear of the 145+ psi heads. His explanation was it puts to much pressure on the stock crank, pistons, rods, ect... and a bearing or worse could go out.

    I am looking for something that will give me some added power but run for almost ever.

    And if anyone has a modded stock head for sell that will be something I would want let me know!

    Thanks!


  2. #2
    I just went through the same questions as you. The best reliable performance seems to be with around 150 psi and 93 octane fuel (less psi for lower octane fuels). Jim did a great job on mine for $85 plus shipping with a quick turn around time. I have no complaints what so ever and would do it again without a second thought.

  3. #3
    Happily Self-Employed WFO's Avatar
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    Jim does awesome head work.

  4. #4
    Chrisrokc's Avatar
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    Quote Originally Posted by WFO View Post
    Jim does awesome head work.
    Jim is great to work with. Smooth transactions. I will keep him in mind.

    What do you think about a stock head milled to 150psi?

    Does it hurt the reliability of the bike? I don't want to have to rip her apart come 80-100 hours after head swap.

    Whats the stock psi?

  5. #5
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Hello Chris you will be fine with the stock head milled, What also helps is the rear dome is staggered.

  6. #6
    Quote Originally Posted by Chrisrokc View Post
    Whats the stock psi?
    I believe mine was 125,125,123 on a warm engine stock.

  7. #7
    Chrisrokc's Avatar
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    Ok, another question! Lol, all these parts I am planning on for this summer and I think I have lost track on what a good goal is. Here is the mod list for this summer....

    This is what I have NOW in hand or installed

    Riva 1200 Grate
    800 Grate if rpms are not high enough
    2005 Pump with 14/20 DY
    Riva Race Filter
    Riva EFI Controller
    Pump Seal
    D-Plate
    Jetworks
    Air hole mods in bucket and hood
    87mm nozzle if the rpms are not high enough
    FF-Plate from Jim


    What kind of speeds from this?



    This is what I am thinking about adding

    VF3 Reeds
    Keyway
    150psi Stock Head from Jim


    What kind of speed from this?


    You guys are horrible for my wallet!

  8. #8
    Everyone gets a little diferent results. I think the weather has the most to do with it along with aplication but if your current mods are set up correctly with no bugs I would think 72-73 with stock ss, stepped sponsons, no shims in tabs (unless needed) and removing the syphon tube and visability stream never hurts, in superman and cool weather.

    With the other mods I would guess 75 with the proper repitch.

    If my math is correct and the ski responds like it should, That setup should allow for a 14/22 and maybe 14/23 prop (in cool weather). It also seems as though every degree pitch increased on the trailing edge has resulted in approx 1mph at a loss of aprox 100 rpms. So if your current setup turns your 14/20 7200 and you can get an extra 200 rpms from the reeds, key and head. That should put you at 7400. Then you could go up 3 degrees on the pitch to a 14/23 and gain approx 3 mph over your current setup and loose 300 rpms to keep you at 7100.

    The second part is more of an educated guess (educated by other members) than the first because the water is to cold to test it yet since I just did all those things. You can loose or gain as much as 200 rpms just from the weather. Others will chime in Im sure.

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