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DT125R FORUM

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  4. Gearbox failure

Gearbox failure

Scheduled Pinned Locked Moved Engine
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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
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    • L Offline
      L Offline
      lllDennis
      wrote on last edited by
      #16
      This post is deleted!
      1 Reply Last reply
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      • 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

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        • L Offline
          L Offline
          lllDennis
          wrote on last edited by
          #18
          This post is deleted!
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          • 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
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            • 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!

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              • 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.

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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
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                  • 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
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                    • 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
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                      • 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
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                        • 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!

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