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    Piston identification

    Okay so I bought a 81 1100 that was rebuilt and parked approx. 12-15 years ago. The PO was not one hundred percent sure but thought that it had a Yosh 1148 kit installed. So I did a little checking and called Yosh R&D in Cali. the casting marks appear to match what they said but that was all the info they could provide, just identifying that they were Yosh pistons.
    I need to see if any one can identify them a little better I need to know what compression these are supposed to be for so I can adjust accordingly for a future turbo application.
    Also the bore measure 2.905" which if I converted that correctly gets me 73.79mm??? right??? is that the size bore for a 1148???

    At the end of the day I need my compression to be as close to 8:1 as I can get. How can I figure my base gasket thickness to achieve this with the info at hand. By the way all else is stock.

    Here are some pics



    Any help would be greatly appreciated.

    #2
    When you start adding thickness to your gasket, be sure you also install slotted cam sprockets.

    Changing the distance from the crank to the cams will affect the cam timing and you will need to correct for that.
    You will probably want to optimize your cam timing for pressurized aspiration, anyway.

    Yes, there is nothing like horsepressure.

    .
    sigpic
    mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
    hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
    #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
    #2 son: 1980 GS1000G
    Family Portrait
    Siblings and Spouses
    Mom's first ride
    Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
    (Click on my username in the upper-left corner for e-mail info.)

    Comment


      #3
      Steve could you elaborate a little on the slotted cam sprockets.
      I have not heard of this yet??

      Comment


        #4
        Their are two bolts for the gear that bolts to the cam. If you elongate/slot the bolt holes, it allows you to change the cam timing To ?? 106deg or ???
        depends on your intended purpose for the motor. Turbo ?

        Comment


          #5
          Those pistons look to be in the 10.5:1 range based on the valve pocket depth.
          Ed

          To measure is to know.

          Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

          Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

          Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

          KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

          Comment


            #6
            Does anyone know if the old Yosh pistons were cast or forged?

            Comment


              #7
              That piston is cast. I believe that most if not all yosh pistons of that era were cast.

              Comment


                #8
                Originally posted by gsryder View Post
                Steve could you elaborate a little on the slotted cam sprockets.
                I have not heard of this yet??
                SqDancerLynn1 said it about as well as I can:
                Originally posted by SqDancerLynn1 View Post
                Their are two bolts for the gear that bolts to the cam. If you elongate/slot the bolt holes, it allows you to change the cam timing ...

                Since the cam chain is a rather fixed length, moving the cylinders and head away from the crank with thicker gaskets will rotate the cams a bit, advancing the timing. There are two holes in each sprocket, through which bolts pass to hold them to the cams. By slotting those holes, the relationship of the sprocket on the cam can be adjusted. Also keep in mind that pressurized intake will require different valve timing, so please do your homework.

                .
                sigpic
                mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
                hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
                #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
                #2 son: 1980 GS1000G
                Family Portrait
                Siblings and Spouses
                Mom's first ride
                Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
                (Click on my username in the upper-left corner for e-mail info.)

                Comment


                  #9
                  I have an extra set if slotted cam sprockets.
                  Those look like 10/25-1 pistons with the flat center.
                  The 1075 (stock) have 72mm pistons and the 1166 are 75 so that sounds about right for a 1148.
                  1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
                  1985 GS1150ES stock with 85 Red E bodywork.

                  Comment


                    #10
                    You'd be best getting a stock barrel and pistons for your turbo...not enough base gaskets to get that down to 8 to 1. That will cause all sorts of other problems with oil leaks and keeping a bunch of gaskets together where there should be just one. Sell that barrel and pistons, can yosh supply rings for it?

                    Randy

                    Comment


                      #11
                      Originally posted by gsryder View Post
                      Steve could you elaborate a little on the slotted cam sprockets.
                      I have not heard of this yet??
                      When you try to degree your cams you will figure it out

                      Comment


                        #12
                        I missed the turbo part
                        Get turbo pistons
                        1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
                        1985 GS1150ES stock with 85 Red E bodywork.

                        Comment


                          #13
                          run it a little below zero deck height to .020 using a copper base gasket.
                          there are no rules stating that you have to run 8.1 for a turbo application.
                          i ran an 1168 flat top@ zero deck height.
                          just around 18PSI and it rock and rolled and lived.
                          be greedy with the timing and cheap gas and higher boost levels and you'll have a pile of molten crap to take pictures of.
                          copper head gasket is a maybe depending on boost levels.
                          o-ringing the top of the liners if you push it.
                          welded crank of course.
                          back cut tranny...everybody knows why.
                          HD cyl. studs is a must.
                          main studs keeps your cases from pushing apart.
                          HD backing plate and keep a check on it or straight cut primary's.
                          i could spend 6 months of your pay...well maybe 3

                          FYI
                          if your not familiar with slotted cam sprockets and lobe centers..
                          do a lot of reading before bolting on instant HP.
                          you will save a lot cash and headaches.

                          Comment


                            #14
                            Did you run the oil through the cylinders or block them off and use overhead oiler?
                            Seems the oil will find a way out with a turbo.
                            1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
                            1985 GS1150ES stock with 85 Red E bodywork.

                            Comment


                              #15
                              Originally posted by chef1366 View Post
                              Did you run the oil through the cylinders or block them off and use overhead oiler?
                              Seems the oil will find a way out with a turbo.
                              i have never used a top end oiler.
                              lil seep.
                              lil weep.
                              kept my leather's shiny

                              Comment

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