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Thread: Piston to wall

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    GPRXP vspec1's Avatar
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    Piston to wall

    What are you guys setting your piston to wall clearance with the Riva Pistons? It says .0025 to .003 in Riva's instructions. Seems kind of tight to me. Anyone know what they are stock? Thanks in advance


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    HORSEPOWER JUNKIE 9secZO6's Avatar
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    I would shoot for .0027 it's apparent that todays alloys used in modern forgings expand no more than the hyperucrapics of the recent past. Gone are the days of .005 piston to wall and engines that sound like a diesel when cold.

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    GPRXP vspec1's Avatar
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    Quote Originally Posted by 9secZO6 View Post
    I would shoot for .0027 it's apparent that todays alloys used in modern forgings expand no more than the hyperucrapics of the recent past. Gone are the days of .005 piston to wall and engines that sound like a diesel when cold.
    Lol, I just sent you a pm, Thanks...... Do you know what they are stock?

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    dnielsen's Avatar
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    .0027 on the Riva pistons. I think stock are like .0035..... I can find this in the shop manual if you really need it. Just had the head off mine and cylinders look perfect. Had around 6-7 % leak down when tested a week ago. Pistons look perfect aswell, has been rode hard.

    EDIT: Forgot to add that the pistons were gas ported before installation.

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    GPRXP vspec1's Avatar
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    Quote Originally Posted by dnielsen View Post
    .0027 on the Riva pistons. I think stock are like .0035..... I can find this in the shop manual if you really need it. Just had the head off mine and cylinders look perfect. Had around 6-7 % leak down when tested a week ago. Pistons look perfect aswell, has been rode hard.

    EDIT: Forgot to add that the pistons were gas ported before installation.
    Thanks, was just curious. When you have the time, no rush. I would just like to know what the manual says. Is your ski stock compression?

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    dnielsen's Avatar
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    Quote Originally Posted by vspec1 View Post
    Thanks, was just curious. When you have the time, no rush. I would just like to know what the manual says. Is your ski stock compression?
    Damn!!!

    Guesed that wrong!!!

    Piston/Cylinder Clearance mm (in)

    New Nominal = 0.024 - 0.056 (.0009 - .0022)
    Service Limit = 0.090 (.004)

    Mine is stock compression...

  7. #7
    HORSEPOWER JUNKIE 9secZO6's Avatar
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    The stock pistons are made by Mahle and though they are forged, they do not seem to have the same density as other pistons I have used. Maybe they do it to keep the rod/piston/ring combo at 1264 grams huh?

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    dnielsen's Avatar
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    Quote Originally Posted by 9secZO6 View Post
    The stock pistons are made by Mahle and though they are forged, they do not seem to have the same density as other pistons I have used. Maybe they do it to keep the rod/piston/ring combo at 1264 grams huh?
    I thought they were like 2764 grams (grin).

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    big john's Avatar
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    stick with the .0025 clearance and break it in right, and you will be good, maybe towards the .003 side if your going to run the dog snot out of it right out of the gate, which is more than likely what will happen....... its so hard to lay off the go lever.......

  10. #10
    West Texas RXP skoepp's Avatar
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    I'm sure you have checked this but be sure to check the ring gap.
    Common for 2nd ring on riva to be to tight.

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