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Thread: reboring increased power?

  1. #1
    Join Date
    Jan 2004
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    UK DEVON
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    101

    reboring increased power?

    hi i have to rebore my z and was wondering if there is an big power increase if i bore it out to the max(what is the one size below the max)? and what are the disadvantages? will i have to rejet?
    n what do you recomend?
    thx
    nipps
    Rides:
    86 Tri z phase 1 wrench report porting n DG pipe (this beast is what really got me into trikes!!)
    84 honda 200 big red
    84 yamaha 225dx
    "To scrout or be scrouted the question remains!!?"

  2. #2
    Join Date
    Oct 2003
    Location
    Watertown, New York 13601
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    3,382
    bore it out to the max! That is a stupid idea.
    1985 YAMAHA TRI-Z 250 sold

    2006 YFZ 450

  3. #3
    Join Date
    Jan 2004
    Location
    UK DEVON
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    101
    thats why i want to know the one under max?
    anyway what would u recomend i bore it out too?
    nipps
    Rides:
    86 Tri z phase 1 wrench report porting n DG pipe (this beast is what really got me into trikes!!)
    84 honda 200 big red
    84 yamaha 225dx
    "To scrout or be scrouted the question remains!!?"

  4. #4
    KASEY's Avatar
    KASEY is offline weee weeee weeeeeeeeeee ! ! ! The day begins with 3WW
    Join Date
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    ARIZONAS BIGGEST TROUBLEMAKER
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    4,250
    the 2 mm's difference between stock and .080 is designed to give the cylinder long life,,, not a big power increase.. going 2mm will not make enough difference to even feel on a stock machine,,, you will get way more bang for the buck with a aftermarket pipe,,,, also if you do bore it out and have a problem instead of going to the next oversize you will be going to the cylinder store for a new cylinder or sleeve,,,,,,

  5. #5
    Join Date
    Dec 2002
    Location
    Kansas
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    2,387
    Yes like Kasey said, you won't notice much increase. Just take it to the machine shop and have it bored to the next available size.

    A pipe and a port and polish job will give it the most bang for the buck. A port and polish while the cylinder is already off would be a great idea if you have the cash. I would say a port job from a respectable engine guy would cost $175-$250.
    I had the RIGHT to remain silent, I didn't have the ability!

  6. #6
    C W. is offline First Time Rider Arm chair racerNew to the board
    Join Date
    Apr 2004
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    Key Largo FL.
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    107

    jugs

    kacy and wrench know there stuf save the jug get a pipe

  7. #7
    Join Date
    Sep 2002
    Location
    Washingtons Crossing, Pa.
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    2,977
    Any time you "overbore" any 2-stroke, you will actually lose power unless you match the ports timing angles back up to the new bore.
    J. Jonny D, --- Quad - Trike relations committee Chairman and all around swell guy.

    Rides: '91 Warrior, '87 TW200, 1984 YTM225DX, 1984 ATC125M, '71 CL350 Scrambler

  8. #8
    Join Date
    Jan 2003
    Location
    Ashland City, TN
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    2,576
    These guys are all right. I think the actual increase would be like 10CC's tops, which like they said will hardly be enough to notice.
    Trikes:
    1973 Honda ATC70-orange!
    (2)1985 ATC70
    1985 Big Red 250
    1985 250R

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