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Thread: ATC 90 too much compression?

  1. 01-02-2015, 06:26 PM #1
    MastaFlyMason
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    ATC 90 too much compression?

    I finally got my ATC to fire up but it wasn't running right so I adjusted the valve clearance. The exhaust and intake were both too tight so I put them to spec and put it all back together. When I went to start it it had tons of compression and was very hard to pull. The second pull it broke my pull rope. Is it possible to have too much compression or is this just how much compression these 90's are supposed to have?
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  2. 01-02-2015, 06:55 PM #2
    atc500x
    atc500x is offline Got The Holeshot Arm chair racerJust too addicted
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    Are you sure the timing is correct?

    1986 ATC500X
    1985 ATC250SX
    1985 ATC200X
    1985 ATC250R
    1986 ATC250R
    1984 ATC250R
    1981 ATC70
    1984 ATC70
    1985 ATC70
    Custom built ATC70 / 250R laydwon swap
    1986 ATC250SX FATCAT
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  3. 01-02-2015, 07:53 PM #3
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    Joseph Farrow
    Joseph Farrow is offline Power User Roostin Away
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    Do you have a stock cam?
    * 1978 ATC 90/180 Pauter PJ1 / Springer "Team BAPP" Bike *

    * 1980 ATC 110/180 "Danny's Machine Works" 3D Sprint Dune Bike *

    * Nicholson 500 Race Bike *

    * HPATC Yamaha RD350 "Big Moe" Trike *
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  4. 01-02-2015, 10:20 PM #4
    MastaFlyMason
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    The valve timing is perfect unless it is 180 degrees off but as it fires up I do not think that is the case. I checked ignition timing and point gap they both look good as well. And yes the cam is stock

    It kind of feels like its yanking back when I pull
    Last edited by MastaFlyMason; 01-02-2015 at 10:33 PM.
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  5. 01-02-2015, 11:15 PM #5
    dabody69
    dabody69 is offline At The Back Of The Pack Arm chair racerFirst time rider
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    My 1980 110 did the same thing, ripped the pull cord out of my hand, check timing again
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  6. 01-02-2015, 11:20 PM #6
    MastaFlyMason
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    Quote Originally Posted by dabody69 View Post
    My 1980 110 did the same thing, ripped the pull cord out of my hand, check timing again
    Valve timing?
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