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1983 XJ750 Engine Swap into a 1982 XJ650 Seca

Discussion in 'XJ Modifications' started by Ddkod, Sep 23, 2025 at 10:05 AM.

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  1. Ddkod

    Ddkod New Member

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    Hello all, I'm planning on picking up a 1983 Maxim engine and swap it into my 650 Seca frame.
    I currently have over 35,000 miles on the engine and some leak internally.

    Seen a motor that has 12k miles on it for 100 bucks and thought why not

    So far this is what I will pick up from the donor bike:

    Motor - 12,000 miles

    Will also pick up just in case;

    Final Drive Shaft
    TCI box and pick up coils

    I have a Motogadet M-unit install currently, so i'm not worried about the wiring harness.
    Also converting to a disc brake over the winter
    Will purchase larget jets for my carbs.

    Is there anything else I need from the donor?

    Please let me know, thanks
     
    Ddkod, Sep 23, 2025 at 10:05 AM
    #1
  2. Simmy

    Simmy Well-Known Member

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    the Maxim has rubber mounts. Make sure you get all the motor mounting hardware for the Maxim.
    The LH side cover (shifter cover) for the Seca and Maxim are different but all your existing Seca stuff will bolt to the new motor.
    If the Maxim had the Atari dash panel you will also need to swap the oil level sending units.
     
    Simmy, Sep 23, 2025 at 10:22 AM
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  3. Ddkod

    Ddkod New Member

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    Okay

    Thank you. Should I also take the transmission/shifter as well? Or my gearing will be fine?
     
    Ddkod, Sep 23, 2025 at 11:28 AM
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  4. Brhatweed

    Brhatweed Well-Known Member

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    Gearing is the same between SECA and Maxim, rear tire diameters are different and the SECA uses electronic tachometer taken from one ign coil.
    I have 49,225 miles on my 1981 750 SECA, no leaks or other major problems.
     
    Brhatweed, Sep 23, 2025 at 12:50 PM
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