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80 SG crankcase w/79 head?

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  • #1

    80 SG crankcase w/79 head?

    Hello all,
    Due to an "incident" I'm looking at 4 bent intake valves. The frame is a 79F from the vin numbers and other clues. In trying to locate replacements I checked the number on the engine and it's 3J6-002442. That would indicate a 80SG engine. The intake valves measure 36mm like a 79 should. Could the PO mixed and matched cases and heads? Would it even work correctly? It would be nice to know when ordering parts in the future.

    Anybody got 4 used 36mm intake valves for sale?

    Graduate of the school of hard knocks.
    Chuck
    79' XS1100F "FrankenCycle"
    Lexington, KY
    Tags: None
  • #2
    Try andreas he's probably got a complete head.

    Save you some work.

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    • #3
      I can't remember the thread, but new valves for the 78/79 head are SIGNIFICANTLY cheaper than the larger valves in the later heads. Seems I remember them being @ $8 a piece somewhere? Maybe someone will chime in.

      As far as if the combination will work.. .yup. Just use the early 2H7 cams instead of the 3H5. With the smaller valved head in a later engine, you'll get better compression than even the stock 78/79 motors due to the higher dome on the later pistons. It should be a runner when you're done.

      Try andreas he's probably got a complete head.
      ... As opposed to your pointy half-filled one?

      Tod
      Last edited by trbig; 12-16-2009, 09:14 AM.
      Try your hardest to be the kind of person your dog thinks you are.

      You can live to be 100, as long as you give up everything that would make you want to live to be 100!

      Current bikes:
      '06 Suzuki DR650
      *'82 XJ1100 with the 1179 kit. "Mad Maxim"
      '82 XJ1100 Completely stock fixer-upper
      '82 XJ1100 Bagger fixer-upper
      '82 XJ1100 Motor/frame and lots of boxes of parts
      '82 XJ1100 Parts bike
      '81 XS1100 Special
      '81 YZ250
      '80 XS850 Special
      '80 XR100
      *Crashed/Totalled, still own

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      • #4
        ... As opposed to your pointy half-filled one?



        L e t
        m e
        e x p l a i n
        i t
        s l o w l y
        f o r
        y o u
        Tod,
        I
        m e a n t
        t h e
        c y l i n d e r
        h e a d !

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        • #5
          Hey CWEBB - When I did my bore out & head re-build this fall I got a complete set of intake & exhaust valves, springs, etc from Andreas - no effort - he had it all & no worries - I'd just take the suggestion & as mentioned he probably has an entire head you can get if you want or at least the parts you need. All is stuff is easy to get & you get the right stuff the 1st time - no worries. Man alive this sounds like a commercial hehe. Just tryin' to help you out & send you in the right direction with the least hassle. - Dan
          '81 XS1100 LH - Midnight Special - been lookin' a long time for this one.
          1179 big bore kit, 80SG motor
          Rebuilt head, valves
          TC Bros Forward Controls (Brass Pegs)
          Tkat Fork Brace
          T.C. Spade Fuse Box
          Dyna Coils & wires
          Mikesxs shocks,controls,& bars (special)
          ISO grips with stelleto ends
          4 into 1 black Bassani exhaust
          Bridgestone Spitfires
          Tuned by Tinman905
          & a will to keep it.

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          • #6
            Like trbig sad, make sure you use the 2H7 cams in the older head, and as per my experience, use the governor assembly (centrifical advance) from a 78-79 engine as well. There IS a difference. I had a 2h7 gov assy in my 80 engine and it would ping like hell at high RPM, until I installed the correct 3J6 gov assy a few months ago.

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