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850 to a 750?!

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    850 to a 750?!

    I lost the motor in my GS850(1979) Suzuki. It is a shaft drive bike. I Just bought a GS750(1979) Suzuki scrap bike. The motor runs great BUT it is chain driven. NOW...my question is...if I switch the engines, carb system, and rear wheel so that the GS850 is now a GS750 chain driven bike...Will this work? OR should I hunt down a GS850 Engine. I would fix the GS750 but the front forks are rusted/bad,the frame has alot of rust, seat ripped and taped up, gas tank leaks and the headlight is broken. The previous owner didn't take care of this bike. Anyways...what is done is done. I think it's best to combine the best of both bikes and make one good GS bike. Both frames look exactly alike so I think it will work, I just want to see if anyone here can give me any "heads up" on it not working so I don't waste a lot of my time. I work tons of hours and don't get enough time in the day to waste like that. Thanks for any help guys/gals!

    #2
    I am not 100 percent sure, but I think you can swap the top ends and pistons between the 750 and 850. You would end up with a shaft drive 750cc engine. Assuming the bottom end of your 850 is in good shape, this could be a very easy thing to do.

    I'm sure someone will chime in here to verify or debunk my theory.


    Good luck....

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      #3
      The 750 engine WILL not fit in the 850 frame There are too many differences between the shaft drive and chain Find another 850 or better yet a 1000G, 1100G motor to put in it

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        #4
        What happened to your 850??

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          #5
          What happened to my GS850?!

          A case of bad luck...that's all. I went for a ride and on my way home it seased up solid and shut off. After getting it home I checked for wiring problems or something blown...then I decided to check the spark plugs. I discovered the problem when I unscrewed one from cylinder 4...a spark plug broke off and went through the velves and carb on that cylinder. I took the engine down to the pistins, cleaned it all up, and reassembled it. THe engine runs freely without the top end but when I put the cylinder head back on and adjust the cams to spec...the bike will not turn over. Top end problem with the cams or sticking valves, I think. I have the top end from a GS750(1979). Will it fit the top end of my GS850(1979)? OR do I have to change the pistins too, add the cylinder block and make the 850 into a 750 as well.

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            #6
            I am almost certain that the head and/whole top end will interchange between 750 and 850. The cases and transmission are different though, so no engine swap. IIRC, the 850 was a bored out 750 engine. The extra cc's were added to compensate for the shaft drive's inherent power loss.

            It may also be possible to rebuild your 850 head with parts from the 750. I don't know if the valves are the same size or not though....

            This top end swap is only possible on the 8 valve engines. The 16 valve engine is too different to swap parts like cylinders and pistons.

            If you have it apart already it wouldn't be hard to set the 750 jugs/pistons into place and see if it would work. If it does look like it'll work then use the carbs from the 750 also because they will be jetted properly for that displacement.

            Good luck...

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              #7
              The 750 & 850 use the same valves & springs so there is no problem swapping parts

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