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  1. #1

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    Squish Clearance Woes (787)

    Hey guys,
    This question goes out to all of you that have experience with adjusting squish clearance and/or head volume (ccs) when using an after market pipe (in my case a Rossier).
    What do you consider the minimum safe squish clearance should be using pump gas (93 octane), 175# compression PPG cut head running a Rossier pipe + Novi 42s? I have run .043" with a stock pipe, 180# compression Westcoast head. This setup was totally reliable and performed very well, but , I just do not have any experience with the Rossier. I know PPG likes .050" on most of their heads.
    Thanks in advance for your advice,
    Robert V


  2. #2
    Moderator RX951's Avatar
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    welcome to the forum

    I've never run a Rossier pipe, but it memory serves me right, recommended squish gap on pump gas 787 rotax is from .047 to .063. and anything less and you need to ensure you run the proper octane to prevent detonation. Which it looks like you do with 93 octane.
    Alot of stock motors can have measurements between 065 and .080 squish clearance [depending on the base gasket]
    If I'm not mistaken also, there are 3 different base gaskets available for the 787 motor, to fine tune your squish. I "think" a .4, .5 & .6. are what most stock motors are and a .2,.3,.4 are available....I think....

    I personally would not go below what you are currently are running. Make sure you have plenty of cooling also to the head to help minimize/prevent deto from heat.

    we've got some ole skool gurus that will chime in shortly that may have run the rossier pipe


    Here is a good thread on squish
    http://www.greenhulk.net/forums/show...ghlight=squish
    Last edited by RX951; 07-11-2008 at 03:06 PM.

  3. #3
    Tool Bag water worx's Avatar
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    Just my opinion...The Rossier is next to worthless & not much better than stock. I would run around .060 squich on pump gas.

  4. #4
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    Quote Originally Posted by s/d-daddy View Post
    Hey guys,
    This question goes out to all of you that have experience with adjusting squish clearance and/or head volume (ccs) when using an after market pipe (in my case a Rossier).
    What do you consider the minimum safe squish clearance should be using pump gas (93 octane), 175# compression PPG cut head running a Rossier pipe + Novi 42s? I have run .043" with a stock pipe, 180# compression Westcoast head. This setup was totally reliable and performed very well, but , I just do not have any experience with the Rossier. I know PPG likes .050" on most of their heads.
    Thanks in advance for your advice,
    Robert V

    I was getting 7390 rpm's out of a Rossier Pipe, with an ADA head with 43cc domes, BRM Buckshot 47's. I ran my squish between .045 -.047, good power, no deto problems, on pump 92 octane gas.

    Now I run a Coffman Pipe, with 39cc domes, some good porting, and I'm at 7765 rpm's, not to noticable increase power wise, squish is the same, 105 octane

    Rossier Pipes work well with high compression, 180-200 lbs, @ .045-.047 squish, pretty safe on 92 octane, worked for me anyway.

    You'll lose power if you go to high on squish clearance.

    Rossier is a good rec pipe, but they don't make enough power for race conditions with choppy water.

    I loved my Rossier when I rec rode on pump gas, raced in the novis 800 class with the Rossier set up, pretty much stayed with everybody, but moving up to the 800 open class, I found, the Rossier set up will not stay with that class.
    Last edited by ski pimp; 07-11-2008 at 03:54 PM.

  5. #5

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    Yes, I realize that the Rossier is not as capable as the Spec II or even a spec I, but, this is just a rec. ski and I had the pipe laying around. Several guys are getting some pretty respectable performance out of Rossier pipe equipted skis. I just do not want to create a tuning monster that requires a jetting change everytime the weather changes 2 degrees. Reliability is very important to me.
    It sounds like .043ish" @ 175# compression might be doable if I am careful with my jetting.
    Robert V

  6. #6
    96XPSS's Avatar
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    Hey Robert...glad you found us!

    Just a FYI...anybody that wants to know about oil...Daddy is your man.

    My head is [email protected] .050" squish...so I bet you could easily go to .045" and be safe.

    BTW Worx...my 96 did 67.1 with the Rossier...7550 with an XO. Pretty worthless I know...

  7. #7
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    Quote Originally Posted by 96XPSS View Post
    Hey Robert...glad you found us!

    Just a FYI...anybody that wants to know about oil...Daddy is your man.

    My head is [email protected] .050" squish...so I bet you could easily go to .045" and be safe.

    BTW Worx...my 96 did 67.1 with the Rossier...7550 with an XO. Pretty worthless I know...
    If this thread was over at PWCToday, bill oneal would be in here along with wax head, and a few others, they would tell you Rossier sux(end of discussion), you argue with them, the post will get locked, and you'll be red flagged by LisaLisa, as a troller, ask me how I know that.............posting over there works on the click system, not on your personal experience that you can share with somones else.

    Rick
    Last edited by ski pimp; 07-11-2008 at 07:20 PM.

  8. #8
    96XPSS's Avatar
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    Quote Originally Posted by ski pimp View Post
    If this thread was over at PWCToday, bill oneal would be in here along with wax head, and a few others, they would tell you Rossier sux(end of discussion), you argue with them, the post will get locked, and you'll be red flagged by LisaLisa, as a troller, ask me how I know that.............posting over there works on the click system, not on your personal experience that you can share with somones else.

    Rick
    Well Rick...I've been there done that with them too. Time always tells. Glad you found a positive alternative place to hang out...

    Robert Q

  9. #9
    PEST!'s Avatar
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    Short Bus Tech nuf said

  10. #10

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    Thanks for the welcome guys and thanks also for your responses to my squish clearance issue!
    I have to thank Matt (pdxrealtor) for turning me on to this site. I don't know, but, I thought this site was 4tec & 4-stroke only. (my loss)
    I recognize alot of names as I read the threads. Names that disappeared from the other site. I wondered what happened to you guys. I'm glad you stayed in the PWC tampering business.
    Robert (96XPSS), thanks for jumipng in here. Your opinion carries alot of weight with me. You have helped alot of novice tuners (me being one of them) make their ski purr.
    Thanks to all of you that share your knowledge,
    Robert V

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