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DT125R FORUM

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  4. Time to change wheels and ...

Time to change wheels and ...

Scheduled Pinned Locked Moved Top End
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  • J Offline
    J Offline
    Jens Eskildsen
    wrote on last edited by
    #19

    A slight rebore shouldn't affect the powervalve ๐Ÿ™‚

    CalumC 1 Reply Last reply
    0
    • J Jens Eskildsen

      A slight rebore shouldn't affect the powervalve ๐Ÿ™‚

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

      @jens-eskildsen Yes it will.

      If the bore is stock (getting rarer these days and not worth assuming) then no, you're right. But once you start going over the first rebore size, modifying the valve is a must.

      To save confusing, I said modify the valve just as a precaution.

      Always Originate, Never Pirate!

      1 Reply Last reply
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      • Y Offline
        Y Offline
        Yegor
        wrote on last edited by
        #21

        Yes, the cylinder was rebored at least once. Now I'm looking where do that again. Thx !!

        @Calum > ?
        0_1512655186767_IMG_20171205_163718.jpg

        CalumC 1 Reply Last reply
        0
        • Y Yegor

          Yes, the cylinder was rebored at least once. Now I'm looking where do that again. Thx !!

          @Calum > ?
          0_1512655186767_IMG_20171205_163718.jpg

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

          @yegor Yeah that's the pup.

          Always Originate, Never Pirate!

          1 Reply Last reply
          0
          • Y Offline
            Y Offline
            Yegor
            wrote on last edited by
            #23

            @Calum **thanks to everyone ** . One question ( maybe a little bit stupid) XD . What material the cylinder is made of ? And the cylinder sleeve ? ( Yamaha DT 125R )

            The cylinder sleeve Iron?
            Cylinder Aluminium ?

            Have you tuned Yamaha cylinder ? ( admision / exhaust transfers etc ?)

            Cheers !

            CalumC 1 Reply Last reply
            0
            • Y Yegor

              @Calum **thanks to everyone ** . One question ( maybe a little bit stupid) XD . What material the cylinder is made of ? And the cylinder sleeve ? ( Yamaha DT 125R )

              The cylinder sleeve Iron?
              Cylinder Aluminium ?

              Have you tuned Yamaha cylinder ? ( admision / exhaust transfers etc ?)

              Cheers !

              CalumC Offline
              CalumC Offline
              Calum
              wrote on last edited by
              #24

              @yegor YEah that's correct. I imagine the bore will be a steel alloy.

              I've had my barrel ported by a tuner.

              Always Originate, Never Pirate!

              declanD 1 Reply Last reply
              0
              • CalumC Calum

                @yegor YEah that's correct. I imagine the bore will be a steel alloy.

                I've had my barrel ported by a tuner.

                declanD Offline
                declanD Offline
                declan
                wrote on last edited by
                #25

                @calum how much did that cost bud and can it just bolt back on no jet changes etc

                CalumC 1 Reply Last reply
                0
                • declanD declan

                  @calum how much did that cost bud and can it just bolt back on no jet changes etc

                  CalumC Offline
                  CalumC Offline
                  Calum
                  wrote on last edited by
                  #26

                  @declan No, porting is going to drastically change the characteristics of a two stroke engine.

                  I wouldn't advise it on a daily, or on stock ignition.

                  You don't get something for nothing. I'm not going into it here, but the principle is, peak almost always alters performance elsewhere, usually torque.

                  There are exceptions where engines are poorly designed and modifications improve performance with no effect. But the end of it is, these engines are pretty well designed. When it comes to porting them, you're making a sacrafice somewhere else in the rev range for more power.

                  Always Originate, Never Pirate!

                  1 Reply Last reply
                  1
                  • Y Offline
                    Y Offline
                    Yegor
                    wrote on last edited by
                    #27

                    Hello ) !
                    I will go tomorrow to the workshop with the cylinder for bore. I know is privileged information and long testing time but do you know where I can find information about tuning cylinder transfers, I think is good idea do something there before it will be bored. Maybe in the same workshop they do that for extra โ‚ฌ, will ask.

                    all this marked with color dots can be modified/enlarged : ?
                    0_1513007430177_cilindro marcado.jpg
                    at the top of ALL the transfers: (?)
                    0_1513007813829_IMG_20171205_163907.jpg

                    so, thank you again for the help, and gas gas !

                    1 Reply Last reply
                    0
                    • CalumC Offline
                      CalumC Offline
                      Calum
                      wrote on last edited by
                      #28

                      Depending on how good your English reading is, I HIGHLY recommend Graham Bell's Two Stroke Performance Tuning.

                      That will give you a lot of knowledge on tuning two strokes.

                      I would NOT recommend porting the barrel, or altering the port timings, without a programmable CDI.

                      Always Originate, Never Pirate!

                      1 Reply Last reply
                      0
                      • Y Offline
                        Y Offline
                        Yegor
                        wrote on last edited by Yegor
                        #29

                        @calum said in Time to change wheels and ...:

                        Graham Bell's Two Stroke Performance Tuning

                        Thanks for the tip Calum . also I have dowloaded the Two-Stroke TUNER'S HANDBOOK By Gordon Jennings. Time to read.
                        ( http://www.2strokeengine.net/gordonjennings/twostroketunershandbook.php )

                        so, for now I'm going to polish a little bit where it is needed , also the power valve , because it is very dirty.
                        Mitaka pistons are good ? where you can buy original Yamaha DT R parts online ( like water pump complete repair kit) ? <--- have find this official site : http://www.recambios-yamaha.com/es/dt125r/2002/bomba-de-agua.html

                        Thank you very much everyone, your answers are very useful.

                        CalumC 1 Reply Last reply
                        0
                        • Y Yegor

                          @calum said in Time to change wheels and ...:

                          Graham Bell's Two Stroke Performance Tuning

                          Thanks for the tip Calum . also I have dowloaded the Two-Stroke TUNER'S HANDBOOK By Gordon Jennings. Time to read.
                          ( http://www.2strokeengine.net/gordonjennings/twostroketunershandbook.php )

                          so, for now I'm going to polish a little bit where it is needed , also the power valve , because it is very dirty.
                          Mitaka pistons are good ? where you can buy original Yamaha DT R parts online ( like water pump complete repair kit) ? <--- have find this official site : http://www.recambios-yamaha.com/es/dt125r/2002/bomba-de-agua.html

                          Thank you very much everyone, your answers are very useful.

                          CalumC Offline
                          CalumC Offline
                          Calum
                          wrote on last edited by
                          #30

                          @yegor I'd recommend PJME, they're based in England but are Two Stroke Specialist, I believe they ship world wide.

                          Polishing will get you so far, gasket matching is going to be far more effective.

                          If you're going for performance, I'd avoid mitaka. Nothing wrong with them, but they are cheap CAST pistons designed to offer a cheap alternative to OEM.

                          For performance, go forged. Grab yourself a forged Wiesco piston and a set of chromium rings.

                          Always Originate, Never Pirate!

                          1 Reply Last reply
                          0
                          • Y Offline
                            Y Offline
                            Yegor
                            wrote on last edited by
                            #31

                            @calum said in Time to change wheels and ...:

                            Grab yourself a forged Wiesco piston and a set of chromium rings.

                            can't find Wiseco ( one ring ?) piston for my model. But in PJME I have find Wossner piston ( 2 rings) , they are good I think, also forged (?)

                            Do you know if in PJME there Wiseco piston for the DT R ?

                            waiting answer from this site . http://www.paramimoto.com/pistones/343-wiseco-piston-yamaha-2-tiempos.html#/piston-dt_125_75_76_684m05600

                            CalumC 1 Reply Last reply
                            0
                            • Y Yegor

                              @calum said in Time to change wheels and ...:

                              Grab yourself a forged Wiesco piston and a set of chromium rings.

                              can't find Wiseco ( one ring ?) piston for my model. But in PJME I have find Wossner piston ( 2 rings) , they are good I think, also forged (?)

                              Do you know if in PJME there Wiseco piston for the DT R ?

                              waiting answer from this site . http://www.paramimoto.com/pistones/343-wiseco-piston-yamaha-2-tiempos.html#/piston-dt_125_75_76_684m05600

                              CalumC Offline
                              CalumC Offline
                              Calum
                              wrote on last edited by
                              #32

                              @yegor Ahh yeah sorry mate, vertex and Wossner are perfectly good forged components, I run Wossner myself, but will be switiching to wiseco for my new engine I'm building.

                              For reliability, I'd stick to twin rings rather than just one.

                              Always Originate, Never Pirate!

                              1 Reply Last reply
                              0
                              • Y Offline
                                Y Offline
                                Yegor
                                wrote on last edited by Yegor
                                #33

                                Hello friends !

                                Finnaly I've recived the piston. While they still fix the cylinder, I am reading carburation manuals and cleaning the Mikuni. I'll buy carburetor jet kit from 180 to 250.

                                I have noticed that the Yamaha piston rings are different while the Wossner ones are the same:
                                0_1514472080448_26177755_10214388893254589_184702224_o.jpg

                                The Small End Bearing is 17mm ( the one that was put ) but the original bearing for Yamaha piston is 19.5 mm, so is very important replace it ?
                                0_1514472465753_26179304_10214388983376842_1813155606_o.jpg

                                And I see that the Wossner piston does not have holes that lubricate the gudgeon pin:
                                0_1514472779932_26237588_10214388991897055_396085839_o.jpg

                                ( it might be a good idea to do them? although I do not think so ) )

                                I have a base gasket but the Genuine Base Gasket it is made of metal (aluminium?) , so It is highly recommended put the metal one ?

                                uf a lot of questions but thank you in advance . :man_biking_tone1:

                                declanD 1 Reply Last reply
                                0
                                • Y Yegor

                                  Hello friends !

                                  Finnaly I've recived the piston. While they still fix the cylinder, I am reading carburation manuals and cleaning the Mikuni. I'll buy carburetor jet kit from 180 to 250.

                                  I have noticed that the Yamaha piston rings are different while the Wossner ones are the same:
                                  0_1514472080448_26177755_10214388893254589_184702224_o.jpg

                                  The Small End Bearing is 17mm ( the one that was put ) but the original bearing for Yamaha piston is 19.5 mm, so is very important replace it ?
                                  0_1514472465753_26179304_10214388983376842_1813155606_o.jpg

                                  And I see that the Wossner piston does not have holes that lubricate the gudgeon pin:
                                  0_1514472779932_26237588_10214388991897055_396085839_o.jpg

                                  ( it might be a good idea to do them? although I do not think so ) )

                                  I have a base gasket but the Genuine Base Gasket it is made of metal (aluminium?) , so It is highly recommended put the metal one ?

                                  uf a lot of questions but thank you in advance . :man_biking_tone1:

                                  declanD Offline
                                  declanD Offline
                                  declan
                                  wrote on last edited by
                                  #34

                                  @yegor as far as I know stock bikes donโ€™t have the metal base gasket I wouldnโ€™t bother with the lubrication hole if it was needed they would of already done it

                                  1 Reply Last reply
                                  0
                                  • CalumC Offline
                                    CalumC Offline
                                    Calum
                                    wrote on last edited by
                                    #35

                                    OEM gaskets are far superior, but Athena gaskets are perfectly good. You MUST use either genuine or Athena for the head gasket. The base gasket doesn't matter.

                                    Be sure to measure the piston ring end gaps on those wossner rings. I have never had a set that were perfect, they've always needed fettling.

                                    Always Originate, Never Pirate!

                                    1 Reply Last reply
                                    0
                                    • terry.tzT Offline
                                      terry.tzT Offline
                                      terry.tz
                                      wrote on last edited by
                                      #36

                                      @yegor said in Time to change wheels and ...:

                                      http://www.2strokeengine.net/gordonjennings/twostroketunershandbook.php

                                      I have read this and I would say read something else after reading it to put information in a better order for understanding

                                      "Muddy water is best cleared by leaving it alone" Alan Watts

                                      1 Reply Last reply
                                      0
                                      • Y Offline
                                        Y Offline
                                        Yegor
                                        wrote on last edited by Yegor
                                        #37

                                        @declan ok thanks, I think the same. But in PJME you can find the Genuine Yamaha base gasket and is the same that I have , made of metal ( I think steel )
                                        http://www.pjme.co.uk/acatalog/4FU-11351-00.jpg

                                        @Calum thx , I will pay attention to ring end gaps. And have bought the Athena head gasket and the original yamaha water pump radial shaft seal.

                                        @terry-tz Thanks , will try read it in English ( I'm from Spain) , and find some literature in spanish.

                                        Now I have disassembled the carburetor and I have understood much better how it works and how they connect the holes. this video helped me a lot:
                                        Chicho Lorenzo ( Lorenzo's father MotoGP)
                                        https://www.youtube.com/watch?v=niNn0LZESfg

                                        My questions are. Our Mikuni carb ( TM 28 ) main original jet is 180 ?
                                        in this webpage you can see specs and the main jet is 180 .
                                        -> https://www.japanbaiku.com/mikuni/mikuni-tm/mikuni-tm28

                                        . Now I have seen that I have 240 all this time , without problems. With the Romeu exhaust will try with 250/260. BUT this jet :
                                        https://www.japanbaiku.com/image/cache/data/chicles_tornillos/kys-00b-500x500.jpg <--- ralenti/starter jet ? the original is 15 . will try 17.5

                                        where do you buy jets kit ? www.japanbaiku.com is a little bit expensive.

                                        Thanks in advance !

                                        CalumC 1 Reply Last reply
                                        0
                                        • Y Yegor

                                          @declan ok thanks, I think the same. But in PJME you can find the Genuine Yamaha base gasket and is the same that I have , made of metal ( I think steel )
                                          http://www.pjme.co.uk/acatalog/4FU-11351-00.jpg

                                          @Calum thx , I will pay attention to ring end gaps. And have bought the Athena head gasket and the original yamaha water pump radial shaft seal.

                                          @terry-tz Thanks , will try read it in English ( I'm from Spain) , and find some literature in spanish.

                                          Now I have disassembled the carburetor and I have understood much better how it works and how they connect the holes. this video helped me a lot:
                                          Chicho Lorenzo ( Lorenzo's father MotoGP)
                                          https://www.youtube.com/watch?v=niNn0LZESfg

                                          My questions are. Our Mikuni carb ( TM 28 ) main original jet is 180 ?
                                          in this webpage you can see specs and the main jet is 180 .
                                          -> https://www.japanbaiku.com/mikuni/mikuni-tm/mikuni-tm28

                                          . Now I have seen that I have 240 all this time , without problems. With the Romeu exhaust will try with 250/260. BUT this jet :
                                          https://www.japanbaiku.com/image/cache/data/chicles_tornillos/kys-00b-500x500.jpg <--- ralenti/starter jet ? the original is 15 . will try 17.5

                                          where do you buy jets kit ? www.japanbaiku.com is a little bit expensive.

                                          Thanks in advance !

                                          CalumC Offline
                                          CalumC Offline
                                          Calum
                                          wrote on last edited by
                                          #38

                                          @yegor Hi bud,

                                          240 main jet is fine, in your climate it probably about right. In colder climates then you would want to up jet slightly.

                                          Jets are expensive, I cannot stress enough how important it is to buy genuine jets from reputable sellers.

                                          Always Originate, Never Pirate!

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