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Thread: Pro-X concerns

  1. #1
    Duke's Avatar
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    Pro-X concerns

    Freind of mine just lost an engine due to ring locator pin falling out. I believe the pin came out due to unproper warm up and full speed pass on a cool morning, piston heated up faster the steel pin causing it to pop. Thats not my concern.

    Cylinders and pistons went to Lowell for repair and sized to new pistons and we found out the piston to bore clearence was at 18 thousandths!!! This is after only 150 hours! Is this normal? I rebuilt my 1200 at 280 something hours and the clearence on the OEM pistons were 10.

    Has anyone checked clearences on the Pro-X after running for a decent amount of time?


  2. #2

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    Cool

    if your bud's bad about warming up ski they he may have
    collapse piston skirt,while ski down have the piston coated will help

    later cd

  3. #3
    Moderator RX951's Avatar
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    After my 100 hour inspection a couple of years ago on my 1200 with Pro-X, I will still fine. I personally have not heard of any pro-x issues on the 1200 platform.

    * Did he put the proper size piston kit in the proper bore ?

    18 thousandths is ALOT

  4. #4
    My Pro x kit and my WSM kit use the same rings ( RIK) I have both kits right here so that should rule any concerns with ring quality out? Z

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    piston's

    The reason the piston ring locating pin came out is the fact that the piston to cylinder clearance became too much causing the top of the piston to flop back and fourth in the cylinder bore shaking the piston ring locating pin out, then ring rotated on piston and when ring end gap lined up with a port opening and it was doomed to fail. Some pistons have shown to have a high rate if shrinkage when heated and cooled over time. The excess piston to cylinder clearance comes from piston shape changing NOT from cylinder bore wear on a Nikisil cylinder. However some steel sleeved cylinders do show more bore wear over time than a plated cylinder. Late 04 and up OEM yamaha pistons were changed to Forged pistons to help elminate this shrinkage problem. This is why the cost of a OEM piston is so high Now. Tommy Jordan
    Last edited by 2fast4u; 12-27-2007 at 11:09 AM.

  6. #6
    Duke's Avatar
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    Quote Originally Posted by 2fast4u View Post
    The reason the piston ring locating pin came out is the fact that the piston to cylinder clearance became too much causing the top of the piston to flop back and fourth in the cylinder bore shaking the piston ring locating pin out, then ring rotated on piston and when ring end gap lined up with a port opening and it was doomed to fail. Some pistons have shown to have a high rate if shrinkage when heated and cooled over time. The excess piston to cylinder clearance comes from piston shape changing NOT from cylinder bore wear on a Nikisil cylinder. However some steel sleeved cylinders do show more bore wear over time than a plated cylinder. Late 04 and up OEM yamaha pistons were changed to Forged pistons to help elminate this shrinkage problem. This is why the cost of a OEM piston is so high Now. Tommy Jordan

    It was a ported 1300 EFI that Lowell set up originally so I'm sure it was perfect.

    Normaly he warms it up better but he was excited about some new found speed and wanted to hammer out a good # first thing.

    I figured it was the piston wearing or collapsing and not the nik wearing. That also makes sense as to why the pin came out. Just seems like excessive wear for that many hours.

    All I run is the new forged OEM piston in my 1300 but thats not an option for the 1200 unported boat.

  7. #7
    ....back from the dead.... J-ME's Avatar
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    Quote Originally Posted by Duke View Post
    It was a ported 1300 EFI that Lowell set up originally so I'm sure it was perfect.
    Not to bad mouth Lowell, but never assume it was set up perfectly. This is the engine builder's ultimate responsibility.

    I have a some cylinders (and pistons)that came from a well known portsmith that had very loose clearances.

  8. #8
    Duke's Avatar
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    Quote Originally Posted by J-ME View Post
    Not to bad mouth Lowell, but never assume it was set up perfectly. This is the engine builder's ultimate responsibility.

    I have a some cylinders (and pistons)that came from a well known portsmith that had very loose clearances.
    Lowell is to much of a perfectionist for "me" to even doubt. Either way the cylinders still check out good. Even if you put an A piston in a D hole the clearence difference is less then a half thousandth.

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    Moderator beerdart's Avatar
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    Quote Originally Posted by Duke View Post
    Lowell is to much of a perfectionist for "me" to even doubt. Either way the cylinders still check out good. Even if you put an A piston in a D hole the clearence difference is less then a half thousandth.
    Do you mean put a D piston into a "A"Hole

  10. #10
    GPRPITMAN's Avatar
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    Duke I know I had a set of pro-x's before where I had the pin go threw the top of piston and then the excess of pin shaved down perfect so pin would not move anymore and lowell did this for me ask him about it.. I did it on my triplepipe

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