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Thread: Calculate CC's

  1. #1
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    Calculate CC's

    How do you calculate the CC's of an engine that's been bored over. My cylinder is be bored to accept a 86.00mm piston (4th over) running on a stock crank. I was just curious as to the CC's of the engine.
    2000 KTM 300 EXC (two stroke heaven)
    1999 Honda 400EX
    Bored to a 406
    Lonestar carrier
    CRF450 timing chain
    1994 Suzuki 250F

  2. #2
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    That would be a 402cc
    2000 Honda TRX400EX ( MX Setup )
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    1986 Suzuki LT-250R ( Stock )
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    2004 Kawasaki KX85 ( Playin Bike )
    199? Yamaha PW80 ( Pit Bike )
    2003 Polaris Trail Boss 330
    1996 Kawasaki Bayou 220

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  3. #3
    Join Date
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    Originally posted by trailrider894
    That would be a 402cc
    86mm piston is a 406, gotta remember the engine itself is designated 400cc but in reality is 397cc.
    If it's stupid, and it works, it isn't stupid. - Murphy's Law
    2000 426EX,sold
    2004 450R WIP
    -Longtime A.A.D.S. (Accessory Acquisition Disorder Syndrome) sufferer.
    400EX Frequently Asked Questions, CHECK HERE FIRST!

  4. #4
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    Originally posted by CJM
    86mm piston is a 406, gotta remember the engine itself is designated 400cc but in reality is 387cc.
    86.5MM is 406cc. From my understanding... on how i did the math.

    Standard bore- 397cc or 85mm

    402cc- .040 over or 86mm

    406cc- .060 ever or 86.5mm

    416cc- .080 over or 87mm

    426cc- .120 over or 88mm

    440cc- .160 over or 89mm

    also...

    440cc with an extra 4mm stroke = 460cc

    416cc with an extra 4mm stroke = 440cc
    2000 Honda TRX400EX ( MX Setup )
    2006 Suzuki LTR450 ( Stock )
    1986 Suzuki LT-250R ( Stock )
    2001 Kawasaki KX250 ( MX Setup )
    2004 Kawasaki KX85 ( Playin Bike )
    199? Yamaha PW80 ( Pit Bike )
    2003 Polaris Trail Boss 330
    1996 Kawasaki Bayou 220

    Proud owner of more than 38 internal combustion engines!!!

    Support our troops and we will support you!!! HOOAH!!!

    Assist, Protect, Defend!!! Military Police!!

  5. #5
    Join Date
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    Right off wisecos site:

    85.5 is 402
    86 is 407 (406 depends on which piston maker)
    If it's stupid, and it works, it isn't stupid. - Murphy's Law
    2000 426EX,sold
    2004 450R WIP
    -Longtime A.A.D.S. (Accessory Acquisition Disorder Syndrome) sufferer.
    400EX Frequently Asked Questions, CHECK HERE FIRST!

  6. #6
    Join Date
    Sep 2010
    Posts
    427
    The formula and math is as follows...

    pi (1/2 bore) ^2 * stroke

    or to make it easier...

    Pi X R X R (R squared) X H

    I'll do it for the 400ex

    So get the bore in cm, divide by 2. 86mm = 8.6cm, /2 = 4.3 square it, = 18.49, times Pi, 18.49 X 3.14159 = 58.08

    58.08 X stroke in cm, 58.08 X 7.0 = 406.56cc's

    The math says a stock stroke with an 86mm piston is 406.

  7. #7
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    Originally posted by rubbersdown
    The formula and math is as follows...

    pi (1/2 bore) ^2 * stroke

    or to make it easier...

    Pi X R X R (R squared) X H

    I'll do it for the 400ex

    So get the bore in cm, divide by 2. 86mm = 8.6cm, /2 = 4.3 square it, = 18.49, times Pi, 18.49 X 3.14159 = 58.08

    58.08 X stroke in cm, 58.08 X 7.0 = 406.56cc's

    The math says a stock stroke with an 86mm piston is 406.
    Hmmm... thanks guys. Not sure how the site i got that from was wrong. Thanks for the new knowledge!!!
    2000 Honda TRX400EX ( MX Setup )
    2006 Suzuki LTR450 ( Stock )
    1986 Suzuki LT-250R ( Stock )
    2001 Kawasaki KX250 ( MX Setup )
    2004 Kawasaki KX85 ( Playin Bike )
    199? Yamaha PW80 ( Pit Bike )
    2003 Polaris Trail Boss 330
    1996 Kawasaki Bayou 220

    Proud owner of more than 38 internal combustion engines!!!

    Support our troops and we will support you!!! HOOAH!!!

    Assist, Protect, Defend!!! Military Police!!

  8. #8
    Join Date
    Feb 2009
    Location
    Wellsburg, WV
    Posts
    139
    Thanks guys. I appreciate the lesson.
    2000 KTM 300 EXC (two stroke heaven)
    1999 Honda 400EX
    Bored to a 406
    Lonestar carrier
    CRF450 timing chain
    1994 Suzuki 250F

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