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gs 750 bottom end and a 850 top

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    gs 750 bottom end and a 850 top

    iv got a 77 gs 750 and i want to put a gs 850 top end on it. iv bin told this is a bolt on but im not sure. what kind of power increase are we talkin? can i use the 850s cylinders and pistons? iv got a buddy with a built up kz 650 and i want to stomp him!

    #2
    The 850 cylinder block will not fit into the 750 cases without cutting the cases a little bit for clearance. Try the wiseco 850 kit. There's enough material in the 750 cylinders for the 4mm overbore.

    Terry

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      #3
      Originally posted by humhead
      The 850 cylinder block will not fit into the 750 cases without cutting the cases a little bit for clearance. Try the wiseco 850 kit. There's enough material in the 750 cylinders for the 4mm overbore.

      Terry
      That's contrary to what I've been told - that is, it's a straight swap. No machining of the crankcases required.

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        #4
        I beg to differ!

        I'm looking the top half of a 750 crankcase with an 850 cylinder block lowered down on the cylinder studs as far as it will go. There's a 3/8 inch gap between the bottom of the cylinders & the top of the case. Turning over the top case half reveals at least four spots where the 850 cylinder block sleeve is making contact with the case.
        I wish it was possible without some machining. The evidence on the floor of my workshop says otherwise.
        If the person who told you it can be done has instructions & pics I'd love to see them. That would mean I'm not out $$ spent on something I can't use.
        The Wiseco 850 kit remains an excellent option. No extra parts necessary.

        Terry

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          #5
          I have heard the 850 cylinders are longer ??? that may be what the hangup is

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            #6
            Re: I beg to differ!

            Originally posted by humhead
            That would mean I'm not out $$ spent on something I can't use.

            Terry
            Me too..... I have a complete 850 top end waiting to go on my 750. I'll not be happy if I have to start grinding things!

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              #7
              have heard the 850 cylinders are longer ??? that may be what the hangup is
              Hmmmm......I'll have to break out the ol' camera and compare blocks.

              I'll not be happy if I have to start grinding things!
              I feel your pain......While the camera is out, I'll see if I can get clear pics of what I'm talking about.

              Terry

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