Big Bore GS1150 on to GS1100

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  • ozgs
    • Jan 2026

    #1

    Big Bore GS1150 on to GS1100

    Hi all,
    I have the oppurtunity to purchase a GS1150 Barrel and MTC 1230 kit. The questions is will this drop onto the otherwise standard 1100 crankcases and will the existing head be suitable?

    Thanks in advance.

    Jon.
  • gearhead13

    #2
    Originally posted by ozgs
    Hi all,
    I have the oppurtunity to purchase a GS1150 Barrel and MTC 1230 kit. The questions is will this drop onto the otherwise standard 1100 crankcases and will the existing head be suitable?

    Thanks in advance.

    Jon.
    An 1150 piston has 20mm pins, and an 1100 has 18mm pins. So the pistons will not fit on your rods unless you put in an 1150 crank.

    Comment

    • ozgs

      #3
      Ok.

      Thanks heaps.

      Comment

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

        #4
        Jon, I have installed at LEAST 50 1150 blocks & 1230 kits on 1100 cases & have only had to do a LITTLE case clearancing on 4 of the 1100 bottom ends. You will only have an issue, if you do at all, where the bottoms of the sleeves slide down into the upper case half. If you are doing a 1230 kit, why not split the cases & install a heavy duty cam chain if you haven't yet? APE case & cylinder studs would be good additions also. Lastly, your head will work fine. Ray.

        Comment

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

          #5
          There is a 1230 block & piston kit on Ebay right now with MTC pistons with 18 mm wrist pins.

          Ray.
          Last edited by rapidray; 04-13-2012, 12:03 AM.

          Comment

          • amxsteve

            #6
            Originally posted by rapidray
            There is a 1230 block & piston kit on Ebay right now with MTC pistons with 18 mm wrist pins.

            Ray.
            I was watching that one and local to mee too

            Comment

            • ozgs

              #7
              Originally posted by rapidray
              There is a 1230 block & piston kit on Ebay right now with MTC pistons with 18 mm wrist pins.

              Ray.
              Thanks Ray. I have bought this item. I will update on how it goes.

              Comment

              • amxsteve

                #8
                Originally posted by ozgs
                Thanks Ray. I have bought this item. I will update on how it goes.
                lucky dog i was out of town

                Comment

                • Roger P.

                  #9
                  I guess it depends on whether they are standard 1150 liners bored our or if thicker aftermarket ones were installed.

                  Comment

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

                    #10
                    Originally posted by ozgs
                    Thanks Ray. I have bought this item. I will update on how it goes.
                    I just went back & looked at the pictures of the ad & I have good news & bad news for you. I never really looked good at them before or I would have given you more information. The good (to ME anyway) is that the block has been resleeved with bigger than stock sleeves. It looks like those are thick enough to go 1260, 1290 or even 1327 if you want. The BAD is that the block has been resleeved with bigger sleeves so you will have to bore your upper case half to clear the bigger sleeves. Not a big deal but a little more expense. The second bad is that those pistons are domed & are probably 12.5-13.5 to 1 compression. NOT the compression you want for a street engine. If you want, call me at 714--356-7845 & I can help you with these issues. Ray.

                    Comment

                    • Guest

                      #11
                      MTC didn't have a lot of pent roof forgings, so there should be plenty of meat to cut the domes off.

                      Comment

                      • ozgs

                        #12
                        Originally posted by rapidray
                        I just went back & looked at the pictures of the ad & I have good news & bad news for you. I never really looked good at them before or I would have given you more information. The good (to ME anyway) is that the block has been resleeved with bigger than stock sleeves. It looks like those are thick enough to go 1260, 1290 or even 1327 if you want. The BAD is that the block has been resleeved with bigger sleeves so you will have to bore your upper case half to clear the bigger sleeves. Not a big deal but a little more expense. The second bad is that those pistons are domed & are probably 12.5-13.5 to 1 compression. NOT the compression you want for a street engine. If you want, call me at 714--356-7845 & I can help you with these issues. Ray.
                        Thanks for the heads up. Would using a thicker base gasket be an option?

                        Comment

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

                          #13
                          An option but not one I would go with. Ray.

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