GS1100 with a 1260 kit.

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  • Roger P.
    • Jan 2026

    #1

    GS1100 with a 1260 kit.

    The recent 1166 dyno results thread got me wondering what hp figures a well-done 1260 mod would produce.

    I'd like a bike with killer roll-on power, without going ape (pardon the pun) with a 1400cc or bigger motor and the heat issues that would result.

    Or I could pick up a decent 10 year old TL or GSXR for around $2000 and reap the suspension and frame upgrade rewards. Probably wouldn't be a fun though, or as comfortable.
  • KiwiGS

    #2
    I would think the cheapest and most reliable way to get "killer roll on" would be to reduce the rolling weight of the bike.
    Modern wheels and suspension etc
    Plus you get the bonus of better tyres, better brakes and better handling.
    Cheers

    Comment

    • Guest

      #3
      With the right head and carbs you could get in the ballpark of 160HP.
      Need a big block though. Can't use your stock cylinder.
      Get an 1150 cylinder you go 1230. Either get some 77mm pistons with 18mm wrist pins or get an 1150 crank and get a 1150 kit.

      Comment

      • Guest

        #4
        Originally posted by Roger P.
        T
        I'd like a bike with killer roll-on power, without going ape (pardon the pun) with a 1400cc or bigger motor and the heat issues that would result.
        Going APE might give you more power than you really want

        Comment

        • Roger P.

          #5
          Well, the guy advertises a stock GS1100 block bored out to accept liners from "LA Sleeve Company". Never heard of them or know what kind of quality I'd be looking at. I also don't know how much meat would be left on the block to transfer the heat from the liners. He's offering a complete kit, pistons, rings,pins,block, upper and lower gaskets for $1000US. Seems like not too bad a deal. I may have sourced some Mikuni flatslides locally, depends on the year of GSXR the guy is parting out, and how much he wants for them. Choke points would be the stock head, cams and pipes, but I figure the size of the motor would make up for a bit of lost hp compared to an 1166 with Web cams, porting and a header.

          Comment

          • Big_T112

            #6
            stock

            I ran my 1260 in a stock cylinde on the street with no problems. It dynoed 168 RWHP with a nice Star racing head. This was on an 1150 motor. I loved the bike and it was a good fun bike to ride.

            Comment

            • rapidray
              Forum Guru
              GSResource Superstar
              • Oct 2006
              • 8195
              • So Cal

              #7
              You can use LA Sleeves as they are good parts. If you want to go 1260 you can do it without going to a big block. You can sleeve the 1100 block or better yet, sleeve an 1150 block for better cooling. I build these all the time & they make GREAT street motors! You can sleeve a stock block to go 1327 but I DON'T recommend it for a daily driver motor. You can bore the 1260 sleeves 2 mm bigger to get a 1327. Ray.

              Comment

              • Roger P.

                #8
                I guess I explained it badly, but the sleeves are already installed and sized to the pistons.

                An APE engine kit would give you the extra bits like cams for a few hundred more. Tough call.

                I guess I'd like to know how long an air cooled motor lasts putting out Hayabusa-like numbers. Is this a yearly tear-down type of deal, or can you expect it to last awhile?

                Comment

                • Guest

                  #9
                  We do 1260s in stock blocks all the time. Plenty of sleeve left, however you wouldn't want to bore 1260 sleeves any larger. We used to haqve a sleeve for 1150 blocks that could go to 1294 when that was the pro stock size limit, but those sleeves are no longer available.

                  Jay

                  Comment

                  • Roger P.

                    #10
                    Hey Jay. I noticed that gszone.biz isn't working any more, at least for me. Server issues?

                    Comment

                    • Guest

                      #11
                      Thanks for the heads up. I just e-mailed the domain people to find out what's up.

                      Jay

                      Comment

                      • jimb12

                        #12
                        If you want to run the 1260 and get the power it's capable of, you'll want to convert the crank/clutch basket to straight-cut gears. 160+ rwhp would be a problem with the angle-cut, my friend blew one with 'just' an 1166. And yes, the basket was modified, not stock.

                        Comment

                        • Guest

                          #13
                          The angle cut gears won't get you more power they just dont force the gears away from each other till things go BOOM!
                          I actually shaved my cases a bit just from helical gears

                          Comment

                          • jimb12

                            #14
                            I wasn't saying it for a power gain, but rather to keep it from blowing up.
                            So actually, it can be worth power, since a running engine beats a blown up one.

                            Comment

                            • Guest

                              #15
                              Originally posted by jimb12
                              I wasn't saying it for a power gain, but rather to keep it from blowing up.
                              So actually, it can be worth power, since a running engine beats a blown up one.
                              You got that right brother!

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