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Thread: will a trx250r engine fit in an 85 atc250r?

  1. #1
    Join Date
    Jan 2005
    Location
    Jones, Michigan
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    1,821

    will a trx250r engine fit in an 85 atc250r?

    Well my engine needs the case welded around the shifter (or just replaced) so im looking on ebay for another engine/case. I know that the 87 and on trx engines were long rod engines but will they fit in my 85 atc250r? Will an 86 trx engine fit?? what engines will and wont work? I just finally got this liquid cooled R so im starting out not knowing much about them.

    Kevin
    "Instruction manuals are nothing more than another man's opinion."
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    -1985 250sx
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    - 1985 atc 250r
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    MADE IT THROUGH TRIKEFEST 04, 05, 06, 07, and 08, cant wait til 09!!

  2. #2
    InPiEcEs's Avatar
    InPiEcEs is offline At The Back Of The Pack Arm chair racerAt the back of the pack
    Join Date
    Apr 2004
    Location
    Northeast Wisconsin
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    378
    Any 250R engine 1985-1989 will bolt into an 85-86 ATC. They are all physically the same. The only issues you will have interchanging stuff is jugs/cranks. The way to get around that is.........if you have a short-rod crank, use a short-rod piston.
    If you have a long-rod crank, use a long-rod piston.
    If you use a long-rod crank, and a short-rod piston, you will need a spacer plate. They moved the piston pin to accomodate the longer rod.
    If you use a short-rod piston on a long-rod crank, the piston will be a few mm to high, because the pin is lower.
    Jugs are all interchangeable, with 88-89? having bridged intakes, which helps against piston skirt cracking a little better.
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  3. #3
    Join Date
    Aug 2006
    Location
    Eugene, Oregon
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    82
    yeah the 88-89 jugs are the same also.

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