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  4. DT 125 R '88... New project

DT 125 R '88... New project

Scheduled Pinned Locked Moved DTR
89 Posts 11 Posters 26.0k Views 1 Watching
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  • CalumC Calum

    @jgr72 Might as well just swap out the engine when you get to that point.

    In my opinion, for the bike you currently own. Leave it as original as possible. It's a gorgeous bike in standard trim, any modifications to it is just criminal if you ask me.

    J Offline
    J Offline
    jgr72
    wrote on last edited by
    #52

    @Calum You're right about keeping this bike original... but since I'm only a human, and I have only one bike that should do all that I want... I will try to keep it look as much original as possible... You simply just can't have too much power... at least this small engine... But to be honest, I can't see very big difference, when accelerating from 0 to 80km/h, when I compare it to my ex XT600... After about 80km/h XT600 would disappear into a horizon...

    Is there a inlet that would rise carb a bit? few centimeters would rise it over the clutch thing... And also inlet should have more angle towards to airbox in order to duck around rear shock...

    I can't even find inlet bolt pattern... It's not so hard job to do by my self... Or it would be nice to know which inlets would fit direct to 3BN engine... Then I could try to find one from somewhere...

    DartyD 1 Reply Last reply
    0
    • J jgr72

      @Calum You're right about keeping this bike original... but since I'm only a human, and I have only one bike that should do all that I want... I will try to keep it look as much original as possible... You simply just can't have too much power... at least this small engine... But to be honest, I can't see very big difference, when accelerating from 0 to 80km/h, when I compare it to my ex XT600... After about 80km/h XT600 would disappear into a horizon...

      Is there a inlet that would rise carb a bit? few centimeters would rise it over the clutch thing... And also inlet should have more angle towards to airbox in order to duck around rear shock...

      I can't even find inlet bolt pattern... It's not so hard job to do by my self... Or it would be nice to know which inlets would fit direct to 3BN engine... Then I could try to find one from somewhere...

      DartyD Offline
      DartyD Offline
      Darty
      wrote on last edited by
      #53

      @jgr72 There are no direct replacement inlets for a DTR engine.

      Believe me I've looked.

      Why don't you try modifying a WR200 inlet? They were made for the Mikuni TM30ss...

      Keep it real

      J 1 Reply Last reply
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      • DartyD Darty

        @jgr72 There are no direct replacement inlets for a DTR engine.

        Believe me I've looked.

        Why don't you try modifying a WR200 inlet? They were made for the Mikuni TM30ss...

        J Offline
        J Offline
        jgr72
        wrote on last edited by
        #54

        @Darty

        I will loose inlet bottle with WR200 inlet!? How much does it effect anyway? Have you any idea how much higher carb will be sitting with WR200 inlet?

        NINJAN 1 Reply Last reply
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        • J jgr72

          @Darty

          I will loose inlet bottle with WR200 inlet!? How much does it effect anyway? Have you any idea how much higher carb will be sitting with WR200 inlet?

          NINJAN Offline
          NINJAN Offline
          NINJA
          wrote on last edited by
          #55

          @jgr72 I lost 10mph from my top speed when I removed my inlet bottle. 😞

          SEDUCED BY THE DARK SIDE!!!

          1 Reply Last reply
          0
          • DartyD Offline
            DartyD Offline
            Darty
            wrote on last edited by
            #56

            @CYBER-NINJA It's werid people say this, A boost bottle and the YIES chamber design from Yamaha never increased horsepower.

            All Boost bottles or 'resonance chambers' do is help to smooth out 2stroke induction, which is of most benefit at lower air speeds... Low to Mid RPM running.

            @jgr72 The WR200 inlet wont raise the height of the carburettor, but, it will make it clear the Clutch arm and give better clearance around the Shock Absorber.

            Also for the love of GOD, do not chop this bike around anymore!!!

            I would get rid of my DTR for your 'Endurance Blue' 3DB1 DT125R. They are one of the most desirable models.

            See my build thread for carb placement, and note that there is no clean way to upsize carburettor bodies!

            EXCEPT. using a (TM30ss) That will just about fit in with the original 125R inlet tract.

            https://dt125r.co.uk/topic/77/yamaha-dt125r-01-running-project/73

            Keep it real

            NINJAN 1 Reply Last reply
            3
            • DartyD Darty

              @CYBER-NINJA It's werid people say this, A boost bottle and the YIES chamber design from Yamaha never increased horsepower.

              All Boost bottles or 'resonance chambers' do is help to smooth out 2stroke induction, which is of most benefit at lower air speeds... Low to Mid RPM running.

              @jgr72 The WR200 inlet wont raise the height of the carburettor, but, it will make it clear the Clutch arm and give better clearance around the Shock Absorber.

              Also for the love of GOD, do not chop this bike around anymore!!!

              I would get rid of my DTR for your 'Endurance Blue' 3DB1 DT125R. They are one of the most desirable models.

              See my build thread for carb placement, and note that there is no clean way to upsize carburettor bodies!

              EXCEPT. using a (TM30ss) That will just about fit in with the original 125R inlet tract.

              https://dt125r.co.uk/topic/77/yamaha-dt125r-01-running-project/73

              NINJAN Offline
              NINJAN Offline
              NINJA
              wrote on last edited by NINJA
              #57

              @Darty Very interesting, I get the tech behind adding the boost bottle and yes it may never increase HP, which was not it's designed purpose as you have correctly stated. All I can do is speak from experience and shared this. By removing it that must have changed the air-flow and the mixture, as the bike was definitely slower with it off. Yamaha obviously did a lot of testing and choose to run this system for optimum performance. All I can say is that the bike ran better with it on, so I kept it on. The only way to really know for-sure is to test with and without the bottle and pick the set-up which gives the best results for your riding style.

              SEDUCED BY THE DARK SIDE!!!

              CalumC 1 Reply Last reply
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              • NINJAN NINJA

                @Darty Very interesting, I get the tech behind adding the boost bottle and yes it may never increase HP, which was not it's designed purpose as you have correctly stated. All I can do is speak from experience and shared this. By removing it that must have changed the air-flow and the mixture, as the bike was definitely slower with it off. Yamaha obviously did a lot of testing and choose to run this system for optimum performance. All I can say is that the bike ran better with it on, so I kept it on. The only way to really know for-sure is to test with and without the bottle and pick the set-up which gives the best results for your riding style.

                CalumC Offline
                CalumC Offline
                Calum
                wrote on last edited by
                #58

                @CYBER-NINJA It was supposed to smooth out a double dip in the harmonics. The bottle resonates at this frequency and forces stored air out of the bottle.

                Always Originate, Never Pirate!

                NINJAN 1 Reply Last reply
                1
                • CalumC Calum

                  @CYBER-NINJA It was supposed to smooth out a double dip in the harmonics. The bottle resonates at this frequency and forces stored air out of the bottle.

                  NINJAN Offline
                  NINJAN Offline
                  NINJA
                  wrote on last edited by
                  #59

                  @Calum The mind boggles at how they came up with the idea in the first place???

                  SEDUCED BY THE DARK SIDE!!!

                  CalumC 1 Reply Last reply
                  0
                  • NINJAN NINJA

                    @Calum The mind boggles at how they came up with the idea in the first place???

                    CalumC Offline
                    CalumC Offline
                    Calum
                    wrote on last edited by
                    #60

                    @CYBER-NINJA Probably physics? And Years of iterations.

                    Always Originate, Never Pirate!

                    1 Reply Last reply
                    1
                    • A Offline
                      A Offline
                      andrewj1680
                      wrote on last edited by
                      #61

                      Ive tried this however the wr200 inlet comes off at a slightly different angle i manage to get it to all go together nice and tight however the carb runs on a angle everytime to open the throttle wide it empties the carb you have to come back off the throttle so it fills back up again, i gave up on the idea of running that carb on a standard dt engine

                      NINJAN 1 Reply Last reply
                      1
                      • A andrewj1680

                        Ive tried this however the wr200 inlet comes off at a slightly different angle i manage to get it to all go together nice and tight however the carb runs on a angle everytime to open the throttle wide it empties the carb you have to come back off the throttle so it fills back up again, i gave up on the idea of running that carb on a standard dt engine

                        NINJAN Offline
                        NINJAN Offline
                        NINJA
                        wrote on last edited by NINJA
                        #62

                        @andrewj1680 Modding is like a jigsaw puzzle, finding the right pieces which fit together takes time and experimentation sadly.

                        SEDUCED BY THE DARK SIDE!!!

                        A 1 Reply Last reply
                        0
                        • NINJAN NINJA

                          @andrewj1680 Modding is like a jigsaw puzzle, finding the right pieces which fit together takes time and experimentation sadly.

                          A Offline
                          A Offline
                          andrewj1680
                          wrote on last edited by
                          #63

                          @CYBER-NINJA i know what you mean which is why i have opted to swap everything including the engine and loom to allow me to get the best out of it

                          1 Reply Last reply
                          0
                          • J Offline
                            J Offline
                            jgr72
                            wrote on last edited by
                            #64

                            DT have been sitting in my garage for some time... But today, I lift it up and changed the front fork seals that I ordered over 6 months ago... Left side had leaked inside the fork boot allready... I decide to fill it up with 15W fork oil... just to make it a bit stiffer... After that I measured the quantity of oil drained out... there was about 750ml (both sides together)... No wonder why it was a bit soft...

                            alt text

                            To make sure that there are something to wait for... I just ordered Athena 170cc kit for my DT :smiling_face_with_heart-eyes:

                            Still need to find new exhaust... Maybe some stainless... Lets see...

                            Irongamer727I 1 Reply Last reply
                            2
                            • O Offline
                              O Offline
                              oldman
                              wrote on last edited by
                              #65

                              I would love to have this bike as it is, seems a shame to not make it original. But thats me I guess, endurance blue a great colour.

                              1 Reply Last reply
                              1
                              • CalumC Offline
                                CalumC Offline
                                Calum
                                wrote on last edited by
                                #66

                                I must admit, this is probably one of my favourite colours for these bikes.

                                Always Originate, Never Pirate!

                                1 Reply Last reply
                                0
                                • J jgr72

                                  DT have been sitting in my garage for some time... But today, I lift it up and changed the front fork seals that I ordered over 6 months ago... Left side had leaked inside the fork boot allready... I decide to fill it up with 15W fork oil... just to make it a bit stiffer... After that I measured the quantity of oil drained out... there was about 750ml (both sides together)... No wonder why it was a bit soft...

                                  alt text

                                  To make sure that there are something to wait for... I just ordered Athena 170cc kit for my DT :smiling_face_with_heart-eyes:

                                  Still need to find new exhaust... Maybe some stainless... Lets see...

                                  Irongamer727I Offline
                                  Irongamer727I Offline
                                  Irongamer727
                                  wrote on last edited by
                                  #67

                                  @jgr72 nice😉

                                  1 Reply Last reply
                                  0
                                  • J Offline
                                    J Offline
                                    jgr72
                                    wrote on last edited by
                                    #68

                                    Few days ago, I took the engine in parts... and this is what I found:

                                    alt text

                                    Thankfully new parts arrived already:

                                    alt text

                                    I tried athena barrel and piston, and it seems that tdc is just as with the earlier barrel & piston.

                                    I will measure both heads and calculate compression ratios just for curiosity...

                                    Still waiting for piston pin bearing to arrive... Old one was just fine, but why not change it to a new one, when it can be done easily...

                                    1 Reply Last reply
                                    2
                                    • CalumC Offline
                                      CalumC Offline
                                      Calum
                                      wrote on last edited by
                                      #69

                                      Doesn't look too bad, barrel should hone nicely, might not need to touch the bottom end.

                                      Always Originate, Never Pirate!

                                      1 Reply Last reply
                                      0
                                      • J Offline
                                        J Offline
                                        jgr72
                                        wrote on last edited by jgr72
                                        #70

                                        Yeah barrel might still be useful... I will store it carefully, so I could return this bike original later if I want...

                                        1 Reply Last reply
                                        0
                                        • J Offline
                                          J Offline
                                          jgr72
                                          wrote on last edited by
                                          #71

                                          @Calum Athena 170cc set fits well into this 3BN engine, there was no problem to install it. Original piston remain about 1-2mm below deck and dome comes just about up to deck hight. Athena piston comes to deck hight and the dome is smaller and comes just over the deck. Athena claims that compression ratio is 13.2 and that is also what I endup by calculating it... combustion chamber is about 13ml and 168cc devided by that is around 13. That's not actually the real CR, since 2T engines start to compress only after the channels in the barrel when piston comes up, damn I didn't measure that part of piston travel...

                                          Next step is to find better solution for TMX30... I ordered from ebay WR200 intake, let's see if it will line the carb better past the rear shock. If not, I may need to build up my own intake... At this point it seems that the DT230 Lanza boot was a waste of money, it does'nt seem to fit in any way... Anyone interested?

                                          I also ordered 170cc version exhaust from Romeu Henriques, let's see how it fits and feels... Silencer will be a gianelli alu silencer...

                                          Anyone have idea, where to start settings of that TMX30? 135 mainjet felt best last autumn... Maybe 140-150 mainjet and needle one step up?

                                          And for all that are oppressing me to keep this as original as possible, that's not happening now... I will store all original parts for later time if I feel to return this original back again...

                                          1 Reply Last reply
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