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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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  • 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 πŸ˜‰

    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 WR200 should have more horisontal angle to avoid rear shock and that joint is originally made for TMX30 carb.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
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    • 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 πŸ˜‰

      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 WR200 should have more horisontal angle to avoid rear shock and that joint is originally made for TMX30 carb.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 Online
      CalumC Online
      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 Online
          CalumC Online
          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!

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          • 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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            • J jgr72

              About a week ago, I bought new project for me πŸ™‚ My plan and idea is to keep this as original looking as possible, and maybe try to get museum register for it. That's why I'd like to change exhaust to as original look as possible... maybe gianelli painted black!? Now bike is running quite well, and papers claim it has 17kw... I think I will just ride the next summer, and take it to parts during next winter...

              here are few photos:

              alt text

              alt text

              CalumC Online
              CalumC Online
              Calum
              wrote on last edited by
              #78

              @jgr72 I'm sure it'll be fine, you went with the big bore kit and the way those boost bottles work is via harmonics. So it's doubtful the frequencies would have been correct anyway.

              Always Originate, Never Pirate!

              1 Reply Last reply
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              • J Offline
                J Offline
                jgr72
                wrote on last edited by
                #79

                Hmm... that's true also... So if I want to use boost bottle, I need to enlarge it about 35% to be in the same as previously 125cc!

                CalumC 1 Reply Last reply
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                • J jgr72

                  Hmm... that's true also... So if I want to use boost bottle, I need to enlarge it about 35% to be in the same as previously 125cc!

                  CalumC Online
                  CalumC Online
                  Calum
                  wrote on last edited by
                  #80

                  @jgr72 I think it's a little more complicated than that. As said it's all to do with Harmonics and the resonance frequency of the engine at a particular motion in the engines cycle.

                  I don't know the specifics in intimate details but the idea is this.

                  At some point in the engines RPM cycle, there is a dip in the air pressure and consequently the engine will perform less than optimally. They characterised this phenomena with a certain frequency. They then created a body with a natural frequency that matches the signature of this phenomena. When the engine hits this frequency, and is down on oxygen, the bottle resonates, forcing reserved air into the inlet tract. This makes up for the loss charge during this period and as a result performance is restored.

                  Now to my mind, there are so many factors that have to be considered that it's either pure genius or pure myth...it's hard to say whether the performance with or without is noticeable, it's probably so slight but the Japs just over engineer it all.

                  Always Originate, Never Pirate!

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                  • CalumC Calum

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

                    Irongamer727I Offline
                    Irongamer727I Offline
                    Irongamer727
                    wrote on last edited by
                    #81

                    @calum was it really worth changing to a 32mm carb? I mean it's only a 4 mm difference from stock? Thought those 28mm mikuni carbs were well up for the job. I'm still running the 28mm with the 170 kit.

                    CalumC 1 Reply Last reply
                    0
                    • Irongamer727I Irongamer727

                      @calum was it really worth changing to a 32mm carb? I mean it's only a 4 mm difference from stock? Thought those 28mm mikuni carbs were well up for the job. I'm still running the 28mm with the 170 kit.

                      CalumC Online
                      CalumC Online
                      Calum
                      wrote on last edited by
                      #82

                      @irongamer727 It's not just the fueling, it's the amount of air you can get in as well. My brother ran a 38mm Keihin carb on his, although to be fair that was probablyt way too big. 32-34 is about right I'd say. The Aprilia RS125 ran 34 as standard and they were making 26-33bhp.

                      Always Originate, Never Pirate!

                      declanD 1 Reply Last reply
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                      • CalumC Calum

                        @irongamer727 It's not just the fueling, it's the amount of air you can get in as well. My brother ran a 38mm Keihin carb on his, although to be fair that was probablyt way too big. 32-34 is about right I'd say. The Aprilia RS125 ran 34 as standard and they were making 26-33bhp.

                        declanD Offline
                        declanD Offline
                        declan
                        wrote on last edited by
                        #83

                        @calum are there any of the aprilia engines that don’t have right hand drive?

                        CalumC 1 Reply Last reply
                        0
                        • declanD declan

                          @calum are there any of the aprilia engines that don’t have right hand drive?

                          CalumC Online
                          CalumC Online
                          Calum
                          wrote on last edited by
                          #84

                          @declan Aprilia didn't make their engines. Just swap the swingarm when you do the engine. Simples.

                          Always Originate, Never Pirate!

                          declanD 1 Reply Last reply
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                          • CalumC Calum

                            @declan Aprilia didn't make their engines. Just swap the swingarm when you do the engine. Simples.

                            declanD Offline
                            declanD Offline
                            declan
                            wrote on last edited by
                            #85

                            @calum well uno out of the Rotax engines but what if it’s an sm

                            CalumC 1 Reply Last reply
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                            • declanD declan

                              @calum well uno out of the Rotax engines but what if it’s an sm

                              CalumC Online
                              CalumC Online
                              Calum
                              wrote on last edited by
                              #86

                              @declan Just get an mx mate, much better bikes.

                              Always Originate, Never Pirate!

                              declanD 1 Reply Last reply
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                              • CalumC Calum

                                @declan Just get an mx mate, much better bikes.

                                declanD Offline
                                declanD Offline
                                declan
                                wrote on last edited by
                                #87

                                @calum ahh okay

                                1 Reply Last reply
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                                • J Offline
                                  J Offline
                                  jgr72
                                  wrote on last edited by
                                  #88

                                  Bike is getting ready for next summer:

                                  alt text

                                  That exhaust chamber :smiling_face_with_heart-eyes:

                                  alt text

                                  Gianelli silencer:

                                  alt text

                                  But need to twist something:

                                  alt text
                                  alt text

                                  I guess it's easier to warm and twist + cat a little bit of that exhaust chamber tail pipe... Gianelli's aluminium would melt away too easily...

                                  1 Reply Last reply
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                                  • CalumC Online
                                    CalumC Online
                                    Calum
                                    wrote on last edited by
                                    #89

                                    Looking lovely, I'd be reluctant to bend the pipe, just make up a larger bracket and move it closer.

                                    Always Originate, Never Pirate!

                                    1 Reply Last reply
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