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Rickman CR900 "GS" engine choice poll - big bore GS550-741/789cc vs GS750-894cc

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    #76
    Aha... thanks for the clarification Ray! I was under the assumption the 750 engine weighed a tad more than the 1000 due to the massively over built crank. 750 8v's do have a much shorter stroke and correspondingly shorter cylinders.
    I yanked the starter motor, starter gears, & starter clutch off my 750 8v, and went as far as to cut the gear off the starter clutch hub so that I could remove all but the bearing that rides on the crank, it order to keep the oil pressure and flow as stock in the crank.

    I weighed the 750 vs 550 engines, with starter motors, and I seem to recall the 750 weighing around 175lbs. I probably posted the bathroom scale weight in this thread. The 550 was about 30 lbs lighter.

    So for that extra 30 lbs of weight, I figured I'd better build this thing to the hilt to make up for a few more pounds. Drop as much weight elsewhere as possible.

    Ray once my house sells, you may likely be receiving 1 each gs850 & gs425 heads from me to get some Serdi valve jobs, bigger valves in the 425 at least, minor porting work, and resurfacing. Probably some cylinders to bore to 71mm as well...


    I'm thinking a 1980+ GS850 head BS32 CV carb head might possibly be a good match for a set of Keihin CR31 smoothbores. I don't want to kill the low end response though. I'll be looking for feedback on this in the near future.

    The vm26 head with smaller intake ports fits vm29 smoothbores well enough, but I wondered really how much gain there was to be had without opening up the intake ports bigher on the vm26 heads.

    Maybe that is the best street engine plan, 29 smoothbores on the 26 head.
    Or maybe the bs32 intake ports will work better for either vm29/CR29 smoothbores AND CR31 smoothbores... ????
    '77 GS750 920cc heavily modded
    '97 Kawasaki KDX220R rugged terrain ripper!
    '99 Kawasaki KDX220R​ rebuild in progress
    '79 GS425stock
    PROJECTS:
    '77 Suzuki PE250 woods racer
    '77 GS550 740cc major mods
    '77 GS400 489cc racer build
    '76 Rickman CR1000 GS1000/1100
    '78 GS1000C/1100

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      #77
      The Rickman fuel tank has a petcock on each side, not sure if 1 is meant to be a reserve or if the are identical, but if identical pickup levels, then the dual fuel feed CR smoothbores win.
      I think there is a flatslide smoothbore Mikuni (FCR?) that also has dual fuel tees. If this user the same jets
      If the Mikuni flatslides use the same main and pilot jets as the VM26/VM29 smoothies & maybe even needles, then those things will get some real serious consideration...
      '77 GS750 920cc heavily modded
      '97 Kawasaki KDX220R rugged terrain ripper!
      '99 Kawasaki KDX220R​ rebuild in progress
      '79 GS425stock
      PROJECTS:
      '77 Suzuki PE250 woods racer
      '77 GS550 740cc major mods
      '77 GS400 489cc racer build
      '76 Rickman CR1000 GS1000/1100
      '78 GS1000C/1100

      Comment

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