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DT125R FORUM

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  4. Gearbox failure

Gearbox failure

Scheduled Pinned Locked Moved Engine
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  • CalumC Offline
    CalumC Offline
    Calum
    wrote on last edited by
    #13

    @DTR-NSR See that death ash on the top as well.

    Always Originate, Never Pirate!

    D 1 Reply Last reply
    0
    • CalumC Calum

      @DTR-NSR See that death ash on the top as well.

      D Offline
      D Offline
      DTR+NSR
      wrote on last edited by
      #14

      @calum yeah it certainly wasn't a happy piston, also was a dark heat spot on the underside of the crown.

      1 Reply Last reply
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      • T Offline
        T Offline
        theportingmaster
        wrote on last edited by
        #15

        @lllDennis Two-stroke piston seizures are either thermal-related or lubrication-failure-related. That one appears to me to be lubrication in nature. Could be overly rich jetting that allowed liquid fuel to wash oil off of the piston skirt as the fuel comes through the transfer ports, causing a lubrication failure.
        If you need a gearbox have a couple of complete low mileage boxes can do you cheap.

        L 2 Replies Last reply
        0
        • L Offline
          L Offline
          lllDennis
          wrote on last edited by
          #16
          This post is deleted!
          1 Reply Last reply
          0
          • T theportingmaster

            @lllDennis Two-stroke piston seizures are either thermal-related or lubrication-failure-related. That one appears to me to be lubrication in nature. Could be overly rich jetting that allowed liquid fuel to wash oil off of the piston skirt as the fuel comes through the transfer ports, causing a lubrication failure.
            If you need a gearbox have a couple of complete low mileage boxes can do you cheap.

            L Offline
            L Offline
            lllDennis
            wrote on last edited by
            #17

            Hey guys thanks for the replies. It's probably the harder break in tha caused the damage. I only had 300km's on it and probably forced it with the top speed run.

            I also opened the gearbox and seem to have stripped a gear. Lots of heat was Involved.
            I included some pictures below. I've never seen damage like this before. Is this normal? 😲

            https://imgur.com/a/BH66681

            1 Reply Last reply
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            • L Offline
              L Offline
              lllDennis
              wrote on last edited by
              #18
              This post is deleted!
              1 Reply Last reply
              0
              • T theportingmaster

                @lllDennis Two-stroke piston seizures are either thermal-related or lubrication-failure-related. That one appears to me to be lubrication in nature. Could be overly rich jetting that allowed liquid fuel to wash oil off of the piston skirt as the fuel comes through the transfer ports, causing a lubrication failure.
                If you need a gearbox have a couple of complete low mileage boxes can do you cheap.

                L Offline
                L Offline
                lllDennis
                wrote on last edited by
                #19

                @theportingmaster The jetting was extremely rich. Apparently there are 2 sorts of mikuni jet 'sizes'. In my carb there was a 250 mikuni jet. So i ordered aftermarket 250-300 for the Athena kit to test with. But the aftermarket 180 size is the same as original 250.

                It was overlay rich while tuning the carb until i figured this out.

                If you got a excellent low milage gearbox for me send me a message with some details. Really appreciate it 👌
                I looked at new original parts but it's a little expensive for my student wallet 😂

                CalumC 1 Reply Last reply
                0
                • L lllDennis

                  @theportingmaster The jetting was extremely rich. Apparently there are 2 sorts of mikuni jet 'sizes'. In my carb there was a 250 mikuni jet. So i ordered aftermarket 250-300 for the Athena kit to test with. But the aftermarket 180 size is the same as original 250.

                  It was overlay rich while tuning the carb until i figured this out.

                  If you got a excellent low milage gearbox for me send me a message with some details. Really appreciate it 👌
                  I looked at new original parts but it's a little expensive for my student wallet 😂

                  CalumC Offline
                  CalumC Offline
                  Calum
                  wrote on last edited by
                  #20

                  @llldennis dayum, that's not a stripped gear, that's completely melted

                  Always Originate, Never Pirate!

                  L 1 Reply Last reply
                  0
                  • T Offline
                    T Offline
                    theportingmaster
                    wrote on last edited by
                    #21

                    @lllDennis Best jetting for Athena 170 is 300 main jet on the
                    Mikuni tm28 but with the powerjet blocked off. Just cut the
                    rubber tube in half from the float chamber to the powerjet then block the 2 halves of the rubber tube with a couple of 5mm threaded bolts or similar.

                    1 Reply Last reply
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                    • CalumC Calum

                      @llldennis dayum, that's not a stripped gear, that's completely melted

                      L Offline
                      L Offline
                      lllDennis
                      wrote on last edited by lllDennis
                      #22

                      @calum Any recommendations on a crankshaft? While everything is open I want to replace it anyway (Has some small grooves where the bearing is). Best with original or aftermarket?

                      CalumC 1 Reply Last reply
                      0
                      • L lllDennis

                        @calum Any recommendations on a crankshaft? While everything is open I want to replace it anyway (Has some small grooves where the bearing is). Best with original or aftermarket?

                        CalumC Offline
                        CalumC Offline
                        Calum
                        wrote on last edited by
                        #23

                        @llldennis Didn't know they do aftermarket cranks?

                        Always Originate, Never Pirate!

                        NottsbikerN jimmydc98J 2 Replies Last reply
                        0
                        • CalumC Calum

                          @llldennis Didn't know they do aftermarket cranks?

                          NottsbikerN Offline
                          NottsbikerN Offline
                          Nottsbiker
                          wrote on last edited by
                          #24

                          @calum

                          There's some on ebay for less than £200

                          jimmydc98J 1 Reply Last reply
                          0
                          • CalumC Calum

                            @llldennis Didn't know they do aftermarket cranks?

                            jimmydc98J Offline
                            jimmydc98J Offline
                            jimmydc98
                            wrote on last edited by
                            #25

                            @calum pretty sure they sell the aftermarket cranks on PJME as well

                            DT200WR 1997 - New Project
                            DTR 125 1997 - The Bike That Got Stolen
                            DTR 125 2002 - Project
                            DT 125 LC 1986 - Old Bike

                            1 Reply Last reply
                            0
                            • NottsbikerN Nottsbiker

                              @calum

                              There's some on ebay for less than £200

                              jimmydc98J Offline
                              jimmydc98J Offline
                              jimmydc98
                              wrote on last edited by
                              #26

                              @nottsbiker https://www.pjme.co.uk/acatalog/Yamaha-DT125R-Complete-Crankshaft-Top-Racing--4596.html#SID=103

                              DT200WR 1997 - New Project
                              DTR 125 1997 - The Bike That Got Stolen
                              DTR 125 2002 - Project
                              DT 125 LC 1986 - Old Bike

                              CalumC 1 Reply Last reply
                              0
                              • jimmydc98J jimmydc98

                                @nottsbiker https://www.pjme.co.uk/acatalog/Yamaha-DT125R-Complete-Crankshaft-Top-Racing--4596.html#SID=103

                                CalumC Offline
                                CalumC Offline
                                Calum
                                wrote on last edited by
                                #27

                                @jimmydc98 Cheap 😍

                                That's good to know at least. Connecting Rod for my RS is that price alone 😛

                                Always Originate, Never Pirate!

                                1 Reply Last reply
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