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DT125R FORUM

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Cylinder questions

Scheduled Pinned Locked Moved Engine
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  • CalumC Calum

    The Athena kits are plated. The stock cylinders are lined with steel bores.

    Irongamer727I Offline
    Irongamer727I Offline
    Irongamer727
    wrote on last edited by
    #3

    @calum I know it's a VERY debated question. But in theory, you mean the Athena kit would need little or no running in?

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    • CalumC Offline
      CalumC Offline
      Calum
      wrote on last edited by
      #4

      It's mating the rings to the cylinder walls. You're forcing dissimilar materials against each other. Not only that, components wear together. Nothing is perfect, so the walls have imperfections, as do the rings. You want to gently mate the two items. When you refresh the rings, you're mating a worn bore to new rings. This will aggravate the components, care must be taken to again mate the components.

      We're talking thousandths of an inch, but at 12,000 rpm, you want to be damn sure they're near perfect.

      Always Originate, Never Pirate!

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      • Irongamer727I Offline
        Irongamer727I Offline
        Irongamer727
        wrote on last edited by Irongamer727
        #5

        So this is the cylinder and perhaps piston I'm going to substitute my Athena kit with.
        The cylinder is in fantastic condition (or so I think) and the piston as well.

        They should be reusable right? No need for a new piston either?

        Piston and cylinder substitute https://imgur.com/a/zldHrxx

        CalumC 1 Reply Last reply
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        • Irongamer727I Irongamer727

          So this is the cylinder and perhaps piston I'm going to substitute my Athena kit with.
          The cylinder is in fantastic condition (or so I think) and the piston as well.

          They should be reusable right? No need for a new piston either?

          Piston and cylinder substitute https://imgur.com/a/zldHrxx

          CalumC Offline
          CalumC Offline
          Calum
          wrote on last edited by
          #6

          @irongamer727 I'd have the bore honed and a new set of rings.

          Those rings looks like they could benefit from being replaced. Grab a new gudgeon pin and small end bearing. Don't forget to replace the circlips.

          Always Originate, Never Pirate!

          Irongamer727I 1 Reply Last reply
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          • CalumC Calum

            @irongamer727 I'd have the bore honed and a new set of rings.

            Those rings looks like they could benefit from being replaced. Grab a new gudgeon pin and small end bearing. Don't forget to replace the circlips.

            Irongamer727I Offline
            Irongamer727I Offline
            Irongamer727
            wrote on last edited by
            #7

            @calum why hone? It's not even worn

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            • Irongamer727I Offline
              Irongamer727I Offline
              Irongamer727
              wrote on last edited by
              #8

              The pictures don't make it far, I'll have to admit.

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              • Irongamer727I Offline
                Irongamer727I Offline
                Irongamer727
                wrote on last edited by
                #9

                Where can I find good rings, a new gudgeon pin and circlips?

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                • 2 Offline
                  2 Offline
                  2stroketerry
                  wrote on last edited by
                  #10

                  Personaly i would get it bored to the next size as don't know how many miles the piston has done. Also regarding the bore you should have the cross hatching from the cylinder being honed but not any vertical up and down scratches like that cylinder has on it. If you don't mind me asking how much is the barrel and piston? How much are you wanting to spend as i have a spare barrel thats been fully ported and a fresh rebore on it to 57.5mm with a Mitaka piston. Also a spare set of rings with it as well as a brand new genuine Yamaha little end bearing. Has a 3MB head with it thats been skimmed and matched to the ported barrel with the correct swish and compression on it and an Athena head gasket with it that has been alterd to suit the 1.5mm larger bore size. Will post some pictures if your interested.

                  Irongamer727I D 2 Replies Last reply
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                  • 2 2stroketerry

                    Personaly i would get it bored to the next size as don't know how many miles the piston has done. Also regarding the bore you should have the cross hatching from the cylinder being honed but not any vertical up and down scratches like that cylinder has on it. If you don't mind me asking how much is the barrel and piston? How much are you wanting to spend as i have a spare barrel thats been fully ported and a fresh rebore on it to 57.5mm with a Mitaka piston. Also a spare set of rings with it as well as a brand new genuine Yamaha little end bearing. Has a 3MB head with it thats been skimmed and matched to the ported barrel with the correct swish and compression on it and an Athena head gasket with it that has been alterd to suit the 1.5mm larger bore size. Will post some pictures if your interested.

                    Irongamer727I Offline
                    Irongamer727I Offline
                    Irongamer727
                    wrote on last edited by
                    #11

                    @2stroketerry I bought an entire engine for £85, the cylinder came with it. I'm thinking about trying this guy. https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F401431331293

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                    • 2 Offline
                      2 Offline
                      2stroketerry
                      wrote on last edited by
                      #12

                      Hi, yes a few people on this forum have had there barrels re bored by him and said his work is good and you won't find anyone cheaper.

                      Irongamer727I declanD 2 Replies Last reply
                      0
                      • 2 2stroketerry

                        Hi, yes a few people on this forum have had there barrels re bored by him and said his work is good and you won't find anyone cheaper.

                        Irongamer727I Offline
                        Irongamer727I Offline
                        Irongamer727
                        wrote on last edited by
                        #13

                        @2stroketerry so it's worth a try?

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                        • 2 2stroketerry

                          Hi, yes a few people on this forum have had there barrels re bored by him and said his work is good and you won't find anyone cheaper.

                          declanD Offline
                          declanD Offline
                          declan
                          wrote on last edited by
                          #14

                          @2stroketerry just out of curiosity how much is that barrel set up for sale for?

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                          • CalumC Offline
                            CalumC Offline
                            Calum
                            wrote on last edited by
                            #15

                            I wpould go to PJME for my stuff.

                            The hone is just a refresh to restore the crosshatching. I disagree about the rebore unless its out of round, but a decent honing place can decide this for you and order the piston in.

                            Always Originate, Never Pirate!

                            Irongamer727I 1 Reply Last reply
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                            • CalumC Calum

                              I wpould go to PJME for my stuff.

                              The hone is just a refresh to restore the crosshatching. I disagree about the rebore unless its out of round, but a decent honing place can decide this for you and order the piston in.

                              Irongamer727I Offline
                              Irongamer727I Offline
                              Irongamer727
                              wrote on last edited by
                              #16

                              @calum £96 for postage with piston, rebore and all that feels pretty good.

                              CalumC 1 Reply Last reply
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                              • Irongamer727I Irongamer727

                                @calum £96 for postage with piston, rebore and all that feels pretty good.

                                CalumC Offline
                                CalumC Offline
                                Calum
                                wrote on last edited by
                                #17

                                @irongamer727 From PJME?

                                Always Originate, Never Pirate!

                                Irongamer727I 1 Reply Last reply
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                                • CalumC Calum

                                  @irongamer727 From PJME?

                                  Irongamer727I Offline
                                  Irongamer727I Offline
                                  Irongamer727
                                  wrote on last edited by
                                  #18

                                  @calum ehhm no, that eBay guy

                                  CalumC 1 Reply Last reply
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                                  • Irongamer727I Irongamer727

                                    @calum ehhm no, that eBay guy

                                    CalumC Offline
                                    CalumC Offline
                                    Calum
                                    wrote on last edited by
                                    #19

                                    @irongamer727 Oh ryt. Well is the piston any good?

                                    I'd recommend PJME as they're the best in the business. Nothing beats the best.

                                    Always Originate, Never Pirate!

                                    Irongamer727I 1 Reply Last reply
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                                    • CalumC Calum

                                      @irongamer727 Oh ryt. Well is the piston any good?

                                      I'd recommend PJME as they're the best in the business. Nothing beats the best.

                                      Irongamer727I Offline
                                      Irongamer727I Offline
                                      Irongamer727
                                      wrote on last edited by
                                      #20

                                      @calum well if it were me I'd just buy new rings, gudgeon pin and small end and use everything.

                                      CalumC 1 Reply Last reply
                                      0
                                      • Irongamer727I Offline
                                        Irongamer727I Offline
                                        Irongamer727
                                        wrote on last edited by
                                        #21

                                        But then it is me so I don't know goodnight

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                                        • Irongamer727I Irongamer727

                                          @calum well if it were me I'd just buy new rings, gudgeon pin and small end and use everything.

                                          CalumC Offline
                                          CalumC Offline
                                          Calum
                                          wrote on last edited by
                                          #22

                                          @irongamer727 Was the piston forged? If it were cast then I'd think twice about reusing it. But if it were forged and there was no obvious signs of wear.

                                          I have done that before, reused piston and rings on a cylinder that saw only a few k. It's absolutely fine. Just if you are thinking about it, a hone rings gudgeon pin, small end and circlips is well worth doing whilst you're there.

                                          If you don't mind whipping the cylinder off again to do these items at their service schedule then it's not really a problem.

                                          Always Originate, Never Pirate!

                                          Irongamer727I 1 Reply Last reply
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