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  1. #1
    Join Date
    Jun 2006
    Location
    wa
    Posts
    323

    Default piston to cylinder wall gap, how much is too much??

    ok so i blew my top end again, time for another rebuild... i was just curious about when i get it bored how much they should bore it? what is exceptable piston to cylinder clearance on a 240 big bore with a wiesco forged piston... i talked to vito's and the said 3 to 3 1/2 thousandths ... does that seem right?
    1998 Yamaha blaster , 240 kit, 3mm stroker
    1983 atc 250r
    1988 trx 250r

  2. #2
    Join Date
    Mar 2006
    Location
    Southern Oregon Coast
    Posts
    1,637

    Default

    .003-.0035 sounds good.. you can run looser, but any tighter is asking for trouble...

  3. #3
    Join Date
    Sep 2007
    Location
    Kansas
    Posts
    2,608

    Default

    ive always bored my forged pistons to 3 thousandths, i believe that cast pistons can be run even tighter than that.
    I dont just want to be another guy, with a pipe and a payment...


    1986 Honda TRX 250r
    1998 Yamaha YZ 125
    1990 Suzuki RM 250
    1986 Kawasaki JS 300
    1986 Kawasaki JS 550

  4. #4
    Join Date
    Mar 2004
    Location
    Land of Oz
    Posts
    485

    Default

    I run mine 4 and sometimes up to 5.
    "Loose is fast"
    88 330R
    06 500R
    86 310R missile
    02 954RR

    Light travels faster than sound. That's why some people appear bright until you hear them speak.

  5. #5
    Join Date
    Dec 2006
    Location
    South Fork,Pa
    Posts
    2,813

    Default

    Quote Originally Posted by siderbox View Post
    I run mine 4 and sometimes up to 5.
    "Loose is fast"

    Loose is fast but, loose also wears fast. Just keep that in mind




    Never argue with an idiot. They'll just drag you down to their level and beat you with experience

  6. #6
    Join Date
    Oct 2004
    Location
    pennsylvania
    Posts
    14,217

    Default

    loose can equal slap...and slap equals kaboom
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    cheapest ^^performance parts online

  7. #7
    Join Date
    Jul 2007
    Location
    Nashua, New hampshire
    Posts
    1,107

    Default

    Id run what it says for the piston.
    1974 Kawasaki h1 500 tripple.
    Racing pipes, .20 Wisecos and Clamp on K&n's

    Sold The Quadracer

    88 blaster
    pwk 34mm carb
    .....................
    1982 250r - After market silencer - wiseco topend- +4 swingarm - 86 Front end -84 or 85 rear plastics and seat.
    2003 polaris predator 500
    uni airfilter
    Fmf Exhaust
    ..............

  8. #8
    Join Date
    Sep 2007
    Location
    Kansas
    Posts
    2,608

    Default

    even with 3 thousandths clearence, my piston seems to make quite a bit of noise. The more metal, the more it will expand, so the bigger piston the looser it needs to be. 3 thousandths has worked for me, but thats because i have let it have plenty of time for break in, because thats pretty tight.
    I dont just want to be another guy, with a pipe and a payment...


    1986 Honda TRX 250r
    1998 Yamaha YZ 125
    1990 Suzuki RM 250
    1986 Kawasaki JS 300
    1986 Kawasaki JS 550

  9. #9
    Join Date
    Mar 2004
    Location
    Land of Oz
    Posts
    485

    Default

    I hear ya fulltiltrider and flotek. I've had good luck with it so far.
    88 330R
    06 500R
    86 310R missile
    02 954RR

    Light travels faster than sound. That's why some people appear bright until you hear them speak.

  10. #10
    Join Date
    Dec 2006
    Location
    South Fork,Pa
    Posts
    2,813

    Default

    Quote Originally Posted by siderbox View Post
    I hear ya fulltiltrider and flotek. I've had good luck with it so far.

    You know, I hear that alot of the guys that run sabre cylinders are running clearances from .007 to as much as .010. I cant imagine being that loose but, those are the guys that are winning, of course they also have the cash to spend when things go bad.




    Never argue with an idiot. They'll just drag you down to their level and beat you with experience