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Thread: Riva Pistons

  1. #1
    RXP 260 X Short Course Veteran RXP244's Avatar
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    Riva Pistons

    Have been running in my engine over the last few days/hours and today was the first time I really had the throttle to the bar for any extended period. Had had some clue that something was different than before, but didn't expect such a big change.

    Engine rebuild consisted of new Riva pistons one size over, new bearings through out and a tidy up on the head. Nothing else. Haven't touched the pump or prop.

    Old numbers were 85-86mph @ 8350-8450rpm. Now the thing is all over the limiter at 8600-8650, so I gonna have to repitch and start again.

    Something tells me my old rings and pistons were past their use by date!


  2. #2
    R88ory RXP's Avatar
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    Quote Originally Posted by RXP244 View Post
    Have been running in my engine over the last few days/hours and today was the first time I really had the throttle to the bar for any extended period. Had had some clue that something was different than before, but didn't expect such a big change.

    Engine rebuild consisted of new Riva pistons one size over, new bearings through out and a tidy up on the head. Nothing else. Haven't touched the pump or prop.

    Old numbers were 85-86mph @ 8350-8450rpm. Now the thing is all over the limiter at 8600-8650, so I gonna have to repitch and start again.

    Something tells me my old rings and pistons were past their use by date!
    Stock compression???

    Has any1 run the 9.5s yet??? I saw that vid the other day but would like some feedback on the 9.5 CR pistons. Esspecially if some1 is running them, with 15-16psi boost. R88

  3. #3
    RXP 260 X Short Course Veteran RXP244's Avatar
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    Yeah, sorry, only the stock comp. With barely anything taken off the head.

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    rick xp's Avatar
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    That really awesome Roscoe.

    Man thats a massive gain.

    Should be in the upper 80's easy as.

  5. #5
    Hey man did you do the rebuild yourself ?

  6. #6
    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by R88ory RXP View Post
    Stock compression???

    Has any1 run the 9.5s yet??? I saw that vid the other day but would like some feedback on the 9.5 CR pistons. Esspecially if some1 is running them, with 15-16psi boost. R88

    I think the 9.5 CR pistons can and will be used for a great setup. The only bad thing, is they only come in stock bore and no oversize at this time, so they can only be put into good bores or basically new block.

  7. #7
    Vern's Avatar
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    Thats a big gain ... any chance you checked compression before and after the rebuild? I would be curious if there was a measurable difference in static compression ...

  8. #8
    RXP 260 X Short Course Veteran RXP244's Avatar
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    Quote Originally Posted by italybooze View Post
    Hey man did you do the rebuild yourself ?
    I had Kevin Geard of SkiMD, here in Auckland NZ, do all of the machine work and assembly of the basic block. And I did the rest. Made sure I had perfect engine alignment (thanks Kev for the alignment tool). Put some new Rotax Racing rear engine mounts in at the same time.

  9. #9
    RXP 260 X Short Course Veteran RXP244's Avatar
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    Quote Originally Posted by Vern View Post
    Thats a big gain ... any chance you checked compression before and after the rebuild? I would be curious if there was a measurable difference in static compression ...

    Didn't have a chance really to do a compression check before rebuild, as I had a piston fail and we stripped the head off straight away to find that prob. The OE pistons were toast and rings were shot, huge amount of movement in the bores. I am just amazed at the amount of rpm I have picked up. Now just got to convert to that to more speed

  10. #10
    dhoad's Avatar
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    Quote Originally Posted by R88ory RXP View Post
    Stock compression???

    Has any1 run the 9.5s yet??? I saw that vid the other day but would like some feedback on the 9.5 CR pistons. Esspecially if some1 is running them, with 15-16psi boost. R88
    I have the 9.5s going in a stock bore motor right now, also running shaved and ported head. Can't wait to see how it performs. SHould have results in a few weeks.

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