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  1. #1
    Budman's Avatar
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    How much to mill?

    I have a 98 Gp1200. I would like to try to get some more power out of it. I was thinking of having the head milled to raise the compression. What compression should I aim for? The premium gas here is 91 octane. Other than that I can get 100 octane av gas but I don"t really want to go that route. I was thinking of trying to get it up to 150 Psi. Will this work with 91 octane. I usually run 40:1 premix with amsoil interceptor. I found a machine shop that will do the milling but I don't know how much to take off. Any advice would be great. My sig shows the mods I have made so far. Also where is a good place that I can order a head gasket. The yamaha dealer here went out of business.
    Thanks
    Budman


  2. #2

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    Not sure on how much to mill. Maybe contact Group K as they use to mill heads and they may still do it.

    Check the middle link on the header of this page for OE replacement parts. Also, any yamaha dealer (even quad/bike dealers) can order parts for our skis. You just need the part #.

  3. #3
    Flying Scotsman's Avatar
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    Pro tec $150 go to there website.

  4. #4
    Budman's Avatar
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    I was thinking of sending it to pro-tec and have it done. But I thought I may save some time and money by having it done here. I talked to a guy that does a lot of mods on motorcycles and he thought 20 thousands would be good but I need to get more opinions.
    Scotty-- I see you run 150 PSI. What octane do you use?
    Budman

  5. #5

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    150 is 93 octane

  6. #6
    Budman's Avatar
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    Do you think I can bump 91 octane up to 93 with gas additives? I see amsoil makes a octane boost.

  7. #7
    Flying Scotsman's Avatar
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    91 octane is fine you can go as high as 165 psi on 93 octane if your carefull and know what your doing.
    A GP can run 89 octane at 150 psi.
    I am still puting my 99 motor together I have to get my squish right then cc my dome.Then I will check comp and go from there.
    150 psi is a reference for now it might be higher or lower because of the big bore and the porting
    I was going to run 100 octane but it looks like I might only need 93 octane with a splash of 100 octane added.
    I wont know till I do my final comp test.

  8. #8
    Budman's Avatar
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    I see in your sig you have a 5 degree nozzle. What exactly is it and what are the benefits. Top speed, hole shot or handling? Also do you think raising the compression from 120 to 150 will make a noticeable difference?
    Budman

  9. #9
    Flying Scotsman's Avatar
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    Quote Originally Posted by Budman View Post
    I see in your sig you have a 5 degree nozzle. What exactly is it and what are the benefits. Top speed, hole shot or handling? Also do you think raising the compression from 120 to 150 will make a noticeable difference?
    Budman
    the 5 deg exit nozzle helps lift the nose up out of the water causing less drag.There is a gain in speed and rpm in good conditions.
    In rough water a 0 deg is usually better.
    Raising compression to 150 psi is abrolutely noticeable I strongly reccomend it.

  10. #10
    Budman's Avatar
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    Rats.... Pro-tec doesn't do heads any more. I will have to talk to the machine shop here. If I only knew how much to have them mill off the head.

    Budman

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