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Motor swaps 900 in a 650?

Discussion in 'XJ Modifications' started by On1wheel01, Jun 11, 2007.

  1. On1wheel01

    On1wheel01 Member

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    Ok I'm trying to figure out what motors from other bikes will fit into my 82 seca 650. Including 750's. As I really wanna do a 750 swap(i think).
     
  2. KiwiXJ750D

    KiwiXJ750D Member

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    Re: Motor swaps

    The 750 fits, people have said a 900 will fit (just). Seca or Max will be OK. It's a direct bolt in.
     
  3. On1wheel01

    On1wheel01 Member

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    Re: Motor swaps

    So a midnight max motor would fit?
     
  4. On1wheel01

    On1wheel01 Member

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    Re: Motor swaps

    Just to see,has if anyone has ever put a 900 motor in a 650 frame. I see old posts from ppl saying it will fit, but the tank may have to be modified(does the frame have to be cut?. Well will the motor bolt right up to the 650 drive shaft? Also would you have to get 900 carbs or would the 650 carbs work? With all this said is their a huge diff in power in the 750 compared to 900? And then theres the exhaust. Do you need 900 exhaust, or 650 ok? Dang I need help.
     
  5. englishsandwich

    englishsandwich Member

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    Well I can't answer all your questions, but I can say that I don't think there is much of a difference in power between the 900 and 750. If I remember right it was a couple hp and 5-8mph. That is purely from memory, I could be wrong.

    As for the carbs: I don't know with the XJ's, but going on my experience with Honda CB's, the carbs are going to have different jets and so on. The exception was the same carbs were used on the 350/400 and the same on the 500/550. Transferring this to an XJ I would think that because there is such a large difference in engine size, it is likely the carbs will need to be changed or at least rebuilt and jetted.

    Someone will likely tell you better than I. I am relatively new to the XJs.
     
  6. englishsandwich

    englishsandwich Member

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    This LINK says that the 650 750 and 900 are interchangeable. I will let you decide if you trust him. Putting a 900 on a 650 turbo may be fun...
     
  7. KiwiXJ750D

    KiwiXJ750D Member

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    Re: Motor swaps

    AFAIR you don't need to cut the frame, it just fits the 900 cylender is longer you see. Bottom end is the same for all 650, 750, 900.

    The 900 has some go in it. More so than the 750. 900 should still be good for 240 Km/hr from posts in a local forum.

    Quote from said forum:
    ajturbo
    27th January 2005, 19:28
    220??? i had mine off the speedo more than once... 2 up in the south island.. on a closed road.....
    i told my mate, he didn't beleave me...... so i told him to take it out and try and do it also... he came back and said that he had done it also!...

    speedo went up to 240k......

    Header pipes are different, longer reach from under the frame to the exaust ports.

    Carbs for the 900 are Mikuni BS36 x 4 so are different.
     
  8. On1wheel01

    On1wheel01 Member

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    Ok great thanx, well now all I have to do is find a 900 motor. From what i'm seeing it is dang hard to find one. But I'm hoping my tranny will hold out till winter. Ill tear her down then, and do the swap. Might have to put some 650 badges on her to. Be one sweet sleeper
     
  9. sabqat9

    sabqat9 New Member

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    Hi everyone,

    I am new to this forum - I think it is great that there is a forum for XJ owners. They are great bikes - reliable, powerful and great to ride.

    Anyways, I was relieved to see this topic on swapping a 900 motor to a 650 frame. My goal has always been to get a hold of a Seca - as I like the straight up motorcycle style instead of the cruiser.

    I am in luck (I think) - I currently own a 82 650XJ Maxim and I think I might have located an 83 900 Seca.

    Now I am thinking of swapping my good and reliable 650 engine into a 900 frame.

    My question is - will the different model years make it possible to swap a 650 engine into a 900 frame? Is this even a good idea. (I know I am downgrading the size of the engine but I am more of a moderate biker that prefers to stick to the 650 engine - not to mention it has taken me forever to find a Seca of any decent shape in my area)

    Any other considerations I should be aware of if I am going to do this modification?

    Thanks in advance for any replies.

    Sab
     

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