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DT125R FORUM

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Best piston

Scheduled Pinned Locked Moved Top End
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  • Irongamer727I Irongamer727

    Anyone heard if KHC pistons? I had one in my DT when I ran stock cylinder. I can only find it on alibaba lol.

    KHC piston, shit or shit? https://imgur.com/gallery/axdthPy

    Glynn123G Offline
    Glynn123G Offline
    Glynn123
    wrote on last edited by
    #11

    @irongamer727 oho don't get my started on K.H.C Pistons, one big mistake was made when putting one in my gas gas, piston rings didn't actually fit the grooves, like at all, and this was a matching set. Rings are made of what must literally be the most brittle type of chinesium. Pretty sure the skirt snapped on the next owner too as he sold it shortly after showing cases of an extremely damaged nikasil bore. Since then I will never buy anything other than a wossner or wiseco, what a mistake that £20 piston was...

    Irongamer727I 1 Reply Last reply
    0
    • Glynn123G Glynn123

      @irongamer727 oho don't get my started on K.H.C Pistons, one big mistake was made when putting one in my gas gas, piston rings didn't actually fit the grooves, like at all, and this was a matching set. Rings are made of what must literally be the most brittle type of chinesium. Pretty sure the skirt snapped on the next owner too as he sold it shortly after showing cases of an extremely damaged nikasil bore. Since then I will never buy anything other than a wossner or wiseco, what a mistake that £20 piston was...

      Irongamer727I Offline
      Irongamer727I Offline
      Irongamer727
      wrote on last edited by
      #12

      @glynn123
      https://imgur.com/gallery/Ovdhjwg

      Here's the state of my old cylinder. Not sure it was because of the piston but this doesn't look very nice at all. There was this horrible knocking/rattling from the cylinder for those who remember. That's why I decided for the Athena really.

      6000km piston https://imgur.com/gallery/Koz7v5j

      Here's the piston, about 6000km on it.
      Looks pretty okay I guess. I've removed some carbon on the top to look for signs of detonation and such. The carbon build-up isn't actually that bad.

      1 Reply Last reply
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      • Irongamer727I Offline
        Irongamer727I Offline
        Irongamer727
        wrote on last edited by
        #13

        On this piston, I can't see any signs of piston slap.

        CalumC 1 Reply Last reply
        0
        • Irongamer727I Offline
          Irongamer727I Offline
          Irongamer727
          wrote on last edited by
          #14

          https://m.alibaba.com/product/60701710970/Motorcycle-Pistons-Rings-For-YAMAHA-TZR125.html?spm=a2706.amp_showroom

          Think I found it, I mean if you buy this shit, you shouldn't be legally allowed to own a motorized vehicle...
          I can only imagine what @Calum must think😉

          1 Reply Last reply
          1
          • Irongamer727I Irongamer727

            On this piston, I can't see any signs of piston slap.

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

            @irongamer727 That new Forged Vertex one I've just got is going to slap like a BIATCH!

            Massive piston to wall clearances.

            It's hard to tell from the finish how decent a piston is, to really appreciate it you have to understand the properties of the alloy they used. This gets above my comprehension level and I leave that to the professionals.

            But in my book, "Tuning For Speed", Irwin explains what type of alloy is best used for each application. And more interestingly, the best places to get such metals. Namely Birmingham England (about 40 minutes drive from me), whilst referencing the company. Bare in mind this chap is from Australia, so the fact he's referencing something from across the globe is pretty impressive.

            Alas, our manufacturing has since long gone. But a good book never the less.

            Always Originate, Never Pirate!

            Irongamer727I declanD 2 Replies Last reply
            0
            • CalumC Calum

              @irongamer727 That new Forged Vertex one I've just got is going to slap like a BIATCH!

              Massive piston to wall clearances.

              It's hard to tell from the finish how decent a piston is, to really appreciate it you have to understand the properties of the alloy they used. This gets above my comprehension level and I leave that to the professionals.

              But in my book, "Tuning For Speed", Irwin explains what type of alloy is best used for each application. And more interestingly, the best places to get such metals. Namely Birmingham England (about 40 minutes drive from me), whilst referencing the company. Bare in mind this chap is from Australia, so the fact he's referencing something from across the globe is pretty impressive.

              Alas, our manufacturing has since long gone. But a good book never the less.

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

              @calum why would you want big clearances? I measured the bore and the piston and the diameter was nearly the same. To tight is not good of course but I can't imagine why a performance engine would want big clearances.

              CalumC 1 Reply Last reply
              0
              • Irongamer727I Irongamer727

                @calum why would you want big clearances? I measured the bore and the piston and the diameter was nearly the same. To tight is not good of course but I can't imagine why a performance engine would want big clearances.

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

                @irongamer727 It's the thermal co-efficients of forged components which is why there are big piston to wall clearances. Forged components will expand much greater than weaker cast components. Which means the gap will close and it will be fine, but this makes it absolutely paramount that you wait for the engine to get up to operating temperature.

                Same thing as my Starlet.

                Always Originate, Never Pirate!

                Irongamer727I 1 Reply Last reply
                0
                • CalumC Calum

                  @irongamer727 It's the thermal co-efficients of forged components which is why there are big piston to wall clearances. Forged components will expand much greater than weaker cast components. Which means the gap will close and it will be fine, but this makes it absolutely paramount that you wait for the engine to get up to operating temperature.

                  Same thing as my Starlet.

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

                  @calum oh now that you say it I remember.
                  I mean I would not be surprised if my previous piston has expanded a bit too much in the cylinder.

                  As you can see on the link there is like a mirror finish in the exhaust and inlet side. I don't have a clue where the ticking/rattling sound came from though.

                  CalumC 1 Reply Last reply
                  0
                  • Glynn123G Offline
                    Glynn123G Offline
                    Glynn123
                    wrote on last edited by
                    #19

                    My wossner was absolutely silent when I first rebuild the Dt, had a barrel bored to match the piston at the recommended tolerances from wossner. Hundred miles on it started getting rattley, it's now pretty piston slappy at the top end but checked 1000 miles on when headgasket went and piston and ring tolerances were perfect haha, makes great power and starts good so I'm not worried, never heard a good running two stroke any better really, it's when they're silent you need to worry haha.

                    1 Reply Last reply
                    0
                    • CalumC Calum

                      @irongamer727 That new Forged Vertex one I've just got is going to slap like a BIATCH!

                      Massive piston to wall clearances.

                      It's hard to tell from the finish how decent a piston is, to really appreciate it you have to understand the properties of the alloy they used. This gets above my comprehension level and I leave that to the professionals.

                      But in my book, "Tuning For Speed", Irwin explains what type of alloy is best used for each application. And more interestingly, the best places to get such metals. Namely Birmingham England (about 40 minutes drive from me), whilst referencing the company. Bare in mind this chap is from Australia, so the fact he's referencing something from across the globe is pretty impressive.

                      Alas, our manufacturing has since long gone. But a good book never the less.

                      declanD Offline
                      declanD Offline
                      declan
                      wrote on last edited by
                      #20

                      @calum only 21 mins from me 😀

                      1 Reply Last reply
                      0
                      • Irongamer727I Irongamer727

                        @calum oh now that you say it I remember.
                        I mean I would not be surprised if my previous piston has expanded a bit too much in the cylinder.

                        As you can see on the link there is like a mirror finish in the exhaust and inlet side. I don't have a clue where the ticking/rattling sound came from though.

                        CalumC Offline
                        CalumC Offline
                        Calum
                        wrote on last edited by
                        #21

                        @irongamer727 Sounds more like glazed bore which is due to incorrect run in procedure.

                        I've switched from Wossner now, after PJME have advised they've started manufacturing their stuff in China.

                        Now China has some of the worlds foremost engineering plants in the world. It's their QC that lets them down.

                        I've now switched.

                        Always Originate, Never Pirate!

                        Irongamer727I 1 Reply Last reply
                        0
                        • CalumC Calum

                          @irongamer727 Sounds more like glazed bore which is due to incorrect run in procedure.

                          I've switched from Wossner now, after PJME have advised they've started manufacturing their stuff in China.

                          Now China has some of the worlds foremost engineering plants in the world. It's their QC that lets them down.

                          I've now switched.

                          Irongamer727I Offline
                          Irongamer727I Offline
                          Irongamer727
                          wrote on last edited by
                          #22

                          @calum have a look at the link😛

                          1 Reply Last reply
                          0
                          • CalumC Offline
                            CalumC Offline
                            Calum
                            wrote on last edited by
                            #23

                            Definiteoy got a fueling issue there.

                            Always Originate, Never Pirate!

                            Irongamer727I 1 Reply Last reply
                            0
                            • CalumC Calum

                              Definiteoy got a fueling issue there.

                              Irongamer727I Offline
                              Irongamer727I Offline
                              Irongamer727
                              wrote on last edited by
                              #24

                              @calum is that cylinder scrap? The piston was 58.4 mm. So I guess it is soon no point boring that cylinder? Not that I will use it again.

                              CalumC 1 Reply Last reply
                              0
                              • Irongamer727I Irongamer727

                                @calum is that cylinder scrap? The piston was 58.4 mm. So I guess it is soon no point boring that cylinder? Not that I will use it again.

                                CalumC Offline
                                CalumC Offline
                                Calum
                                wrote on last edited by
                                #25

                                @irongamer727 You can go overbore. Really need to modify the valve when you do. And you can have a new liner put in.

                                Always Originate, Never Pirate!

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