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Boring-out 650 Cylinders

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    Boring-out 650 Cylinders

    Just for curiosity sake...What would be a better bang-for-your-buck: Overbore the cylinders on an existing 650 or purchasing a decent 750/850 motor and doing a swap?

    Cost/effort vs. HP gains?

    I don't plan on doing it, but looked into it when I was rebuilding an RZ350 15yrs. ago
    1982 GS650e - Cafe or Scrambler...that is the question...

    #2
    Since you have a 650E, that increases the odds a bit, but I don't think the 750 will fit in the 650 frame.

    And don't even think of the 850 engine. All GS850s are shaft-driven, your frame simply is not set up for that.

    .
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    hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
    #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
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      #3
      This exact same question comes up every few years.. same answer, see above. bigger engines, and even more importantly, the exhaust pipe spacing will not fit the frame.

      besides, the 650E has the most efficient combustion chamber, piston, and head design of any of the two valves per cylinder engines. It makes the same horsepower or actually one more than an 8 valve 750. Right now for $200 shipped from Japan, you can get the GS650 stock OEM style cast pistons in a budget aftermarket big bore kit for 740cc. So a stock 650 makes the same horsepower as a 750, what do you think a 740cc big bore 650 will make? Just don't put on too big of tires and do hard launches, that's a lot of power through a stock engine!
      Last edited by Chuck78; 05-14-2020, 12:42 AM.
      '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
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      '76 Rickman CR1000 GS1000/1100
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