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  1. #1
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    Piston/cylinder wall clearance pjs T-3 550

    Curious what the clearance should be.I was thinking .008 - .010.I have a set of Dycorp twins and a mrd mechanical fuel injection system I plan to try to use for this set-up even with all the bad press.It will be running forged pistons.I have yet to aquire a cylinder and head.I'm wondering what compression is going to be healthy with this set up.The cylinder i'm looking at is new and includes new pjs pistons @ the standard bore,But the owner is saying the piston-cylinder wall clearance is .015 which seems like a lot.Is it possib;e that a full tilt race T-3 engine would need that much?Thx for any input.

  2. #2
    resident guru 440duster's Avatar
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    Re: Piston/cylinder wall clearance pjs T-3 550

    forged pistons require more clearance automotive world because of their expansion characteristics, i would think the same for two strokes but cannot say for sure.
    1984 JS 440
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  3. #3
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    Re: Piston/cylinder wall clearance pjs T-3 550

    I'm aware of that.Just as boats/watercrafts require additional clearence than land engines if they pull in continues fresh water.From what I know cast pistons need .003-.006 and forged need .005-.008 or abouts on marine engines.But a very righ revving,high compression need more because of heat,etc.

  4. #4
    PWCToday.com Is My Home Away From Home john zigler's Avatar
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    Re: Piston/cylinder wall clearance pjs T-3 550

    i would go in the .008 to .010 range.
    RCJS also doing business as WATCON
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  5. #5
    resident guru 440duster's Avatar
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    Re: Piston/cylinder wall clearance pjs T-3 550

    i never know what is the same as 4 stroke stuff. i suppose it really depends on what rpms you would be running and for how long at a time for the .015 to be ok. seems .008-.010 is the way to go
    1984 JS 440
    1990 Superjet 650

    -It is impossible to argue with ignorance-

  6. #6
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    Re: Piston/cylinder wall clearance pjs T-3 550

    Hey John I sent you an email about those parts just now.Thx again

  7. #7
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    Re: Piston/cylinder wall clearance pjs T-3 550

    As I said I agree with you and john totally.Imo .015 would cause piston slap and possible piston breakage.Has anyone actually ran this much without issues?I wonder why this cyliner has been set up like that.Btw It's suppost to be one of jacobs back up cylinders.




    Quote Originally Posted by 440duster View Post
    i never know what is the same as 4 stroke stuff. i suppose it really depends on what rpms you would be running and for how long at a time for the .015 to be ok. seems .008-.010 is the way to go

  8. #8
    PWCToday.com Is My Home Away From Home john zigler's Avatar
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    Re: Piston/cylinder wall clearance pjs T-3 550

    my carbed T-3, with 180 psi is at .008
    RCJS also doing business as WATCON
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    email watcon@watcon.com

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    used parts www.rockcountyjetski.webs.com
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  9. #9
    Top Dog Romoland Jet Rider's Avatar
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    Re: Piston/cylinder wall clearance pjs T-3 550

    dont weiscos have a larger clearance?

    and did you receive the pipes and mrd yet?
    RyAn


  10. #10
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    Re: Piston/cylinder wall clearance pjs T-3 550

    Yes they do require more clearance as they are forged. I did get that today,Just hadn't got around to emailing you.Everything looks good.I'm hoping to drop off the pipes and the broken nut/pump driver to my machinist tomarrow.Thx again!



    Quote Originally Posted by Romoland Jet Rider View Post
    dont weiscos have a larger clearance?

    and did you receive the pipes and mrd yet?

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