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

DT 125 R '88... New project

Scheduled Pinned Locked Moved DTR
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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
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            • 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
                              1
                              • CalumC Offline
                                CalumC Offline
                                Calum
                                wrote on last edited by
                                #72

                                Sounds like you caught the tuning bug, very serious this is.

                                I am surprised you needed a bigger inlet for such a small carb. You can get reducers to fit.

                                Always Originate, Never Pirate!

                                J 1 Reply Last reply
                                0
                                • CalumC Calum

                                  Sounds like you caught the tuning bug, very serious this is.

                                  I am surprised you needed a bigger inlet for such a small carb. You can get reducers to fit.

                                  J Offline
                                  J Offline
                                  jgr72
                                  wrote on last edited by jgr72
                                  #73

                                  @calum said in DT 125 R '88... New project:

                                  Sounds like you caught the tuning bug, very serious this is.

                                  I've had it since 1987 😉

                                  I am surprised you needed a bigger inlet for such a small carb. You can get reducers to fit.

                                  TMX30 will fit quite well to original joint, but the angle is bad... WR200 should have more horisontal angle to avoid rear shock and that joint is originally made for TMX30 carb.

                                  CalumC 1 Reply Last reply
                                  0
                                  • J jgr72

                                    @calum said in DT 125 R '88... New project:

                                    Sounds like you caught the tuning bug, very serious this is.

                                    I've had it since 1987 😉

                                    I am surprised you needed a bigger inlet for such a small carb. You can get reducers to fit.

                                    TMX30 will fit quite well to original joint, but the angle is bad... WR200 should have more horisontal angle to avoid rear shock and that joint is originally made for TMX30 carb.

                                    CalumC Offline
                                    CalumC Offline
                                    Calum
                                    wrote on last edited by
                                    #74

                                    @jgr72 So I'm running a Dellorto VHSA 32mm on stock inlet manifold with no issues.

                                    Always Originate, Never Pirate!

                                    Irongamer727I 1 Reply Last reply
                                    0
                                    • J Offline
                                      J Offline
                                      jgr72
                                      wrote on last edited by jgr72
                                      #75

                                      WR200 inlet did the trick I need:

                                      alt text

                                      Air filter barely misses the rear shock and frame...

                                      Now need to modify those inlet attachment bolt holes to make it fit into crankcase...

                                      Maybe I will loose some bottom torque due to the missing boost bottle!?

                                      CalumC 1 Reply Last reply
                                      2
                                      • J jgr72

                                        WR200 inlet did the trick I need:

                                        alt text

                                        Air filter barely misses the rear shock and frame...

                                        Now need to modify those inlet attachment bolt holes to make it fit into crankcase...

                                        Maybe I will loose some bottom torque due to the missing boost bottle!?

                                        CalumC Offline
                                        CalumC Offline
                                        Calum
                                        wrote on last edited by
                                        #76

                                        @jgr72 Personally I'd want to keep the boost bottle. Whether it actually does anything though as you say.

                                        They did have boost bottles on some WR models. I think it's more useful on road going bikes.

                                        Always Originate, Never Pirate!

                                        1 Reply Last reply
                                        0
                                        • J Offline
                                          J Offline
                                          jgr72
                                          wrote on last edited by
                                          #77

                                          Yeah, I'd like to have it too... It have been there for a reason... Okey, maybe I need to try to find such a WR inlet that have boost bottle! This bike will be used 99% on sand or asfalt roads...

                                          1 Reply Last reply
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