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  1. #1
    Rampage's Avatar
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    Question Any recommendations for pistons/head?

    I need new pistons and a new head for my GP1200R. I found Pro-X pistons for $102 a kit which seems like a good deal. I have read that WSM products are pretty much junk, but on the other hand they are really quite cheap. What should I do for a new head? The one I have now is cut to 150 psi, do I need to be worried about that if I buy a new OEM head? I would like to keep the performance of the cut head...but that means I am looking to spend around $400 for ADA, RIVA, or R&D right? Also, do new heads come with the gaskets and stuff? Thanks guys


  2. #2
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    from what i have been told, the oem pistons are the best option to use, especially if your going to port you motor later as the prox pistons have a narrower skirt on them which may create problems with opened up exhaust inlets/outlets ( done during porting).

    same goes for the head, use an OEM one cut to the correct compression you want as its one piece and not prone to flexing like the 3 piece ones are.

    i used oem pistons, rings, oem cut head (to 155psi) and an eom crank in my last rebuild for those reasons.

    sometimes OEM is just better.

    ps: i was using pro-x 1300cc jugs on the previous build and they did 50-80 hours on a non ported setup without any problems at all.



    Ask lowell or woody if you want a more detailed explanation.

  3. #3
    Rampage's Avatar
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    well I don't really have plans to do any porting, even then the OEM ones are the best route to go? How much is it to have an OEM head cut? If I don't have it cut I think that my ski will be WAY underpowered to spin a 14/20 prop Do I just order the OEM parts from Jerrys store or is there some other website you recommend?

  4. #4
    Moderator beerdart's Avatar
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    I have used pro-x pistons without issues.

  5. #5
    SpeedJunky's Avatar
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    I have ran the pro-x pistons in both my skis and had no issues.
    Pro-x are a little heavier than stock but easier on the wallet.

    put a WTB add in the classified section for the head, bet you will find one quickly.

  6. #6
    Rampage's Avatar
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    I never thought about it before now, but will I need one size bigger pistons after honeing the cylinder? Or will it be fine.

  7. #7

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    Look around there are plently of 1200 heads cheap...I found an ADA head on ebay for $50.

    You can make plently of power with the stock head. Actually the ADA head I have now 150psi didn't add any rpm gain...just added some accelleration.

    On the stock head you can pull the center layer out of the 3 piece gasket to tighten the squish some and raise compression slightly. I did that and then found a local machine shop to just mill I think it was only .015 or .020" off for about $50. Thats about all you can safely mill off before getting into the squish band. Ran great this way.

    I'd rather spend the money on other things that make huge rpm gains like VF3 reeds 100rpm+ gain right there. Or for not much more get it ported while its apart. I'm doing that to a spare 1200 top end and will document before and after porting gains on a 1200 single pipe since I have found no information on yet.

    Also if you can find a pro-tec modded Oem ignition cheap it will give great gains. If protec still does the mod it was only about $155. I gained 60rpm from it but I already had a keyway installed so the gains might be more on your ski.

    You can check out my thread... alittle more radical but it shows that a 1200 can spin a 14/20 prop easily and can fly.

    http://www.greenhulk.net/forums/showthread.php?t=121360

  8. #8
    Rampage's Avatar
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    thanks for the info. I do know that it can spin a 14/20 but with my mods I fear that I will put too much stress on the engine, especially after losing the higher compression.

  9. #9
    Rampage's Avatar
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    another issue that I came across was with my cylinders. I was in the process of ordering new pistons and I know that I need to look at the cylinders for the number on them that correspond to the correct kit that I need to order, but my first cylinder has two numbers on it. While looking at the big pipe, on the PV side and at the top of the cylinder there is a 10 on the left side, and a 0 on the right side. On the second and third cylinders both the numbers are on the right side (4 and then 16). Anyone have any idea on how I would have two numbers on the first one, and which one I should use to order the right kit?

  10. #10

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    Quote Originally Posted by Rampage View Post
    thanks for the info. I do know that it can spin a 14/20 but with my mods I fear that I will put too much stress on the engine, especially after losing the higher compression.
    I would think there would actually be less stress on the engine with lower compression. If it still turns the prop near the same rpm then your good.

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