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DT125R FORUM

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  4. Hello forum, I'm new here, I would appreciate the help.

Hello forum, I'm new here, I would appreciate the help.

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  • C Offline
    C Offline
    Calum
    wrote on 27 Feb 2025, 10:06 last edited by
    #5

    There is no memory in the CDI to my knowledge.

    A weak battery will cause issues with the powervalve, so will things like fault rectifier and bad stator etc.

    But just wanted to start simple.

    Have a look at @scrimsmustang guide on derestricting your model.

    https://www.slideshare.net/slideshow/derestricting-the-yamaha-dt125-r-1988-through-to-2007-scrimsmustangs-classic-yamaha-restorations/32127545

    Always Originate, Never Pirate!

    F 1 Reply Last reply 27 Feb 2025, 16:45
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    • M Offline
      M Offline
      MadGyver
      wrote on 27 Feb 2025, 14:00 last edited by
      #6

      Is the power valve correctly aligned,if it has the diamond shaped base?

      I need my tools and a pile of junk.....

      F 1 Reply Last reply 27 Feb 2025, 16:50
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      • C Calum
        27 Feb 2025, 10:06

        There is no memory in the CDI to my knowledge.

        A weak battery will cause issues with the powervalve, so will things like fault rectifier and bad stator etc.

        But just wanted to start simple.

        Have a look at @scrimsmustang guide on derestricting your model.

        https://www.slideshare.net/slideshow/derestricting-the-yamaha-dt125-r-1988-through-to-2007-scrimsmustangs-classic-yamaha-restorations/32127545

        F Offline
        F Offline
        facundo duarte
        wrote on 27 Feb 2025, 16:45 last edited by facundo duarte
        #7

        @Calum Well I have news, I tried what you told me about disconnecting the PV after its cleaning cycle, however the problem persists. On the other hand, I connected the reed switch wanting to cause the limitation to remove it again (I know it doesn't make sense but I didn't know what to try). There were no changes either, but here's the surprise, since the symptom seems to be electrical but it is also confusing with a rich mixture at high speeds, I tried unplugging the black plastic bottle that is screwed to the frame on the left side and there the following happened, as expected, when leaving, especially at low rpm, it felt thin but to my surprise at high rpm it went to the red line (I had never done that) I did around 80mph at 10k, obviously air enters in excess and it does not make the best carburetion but without that plastic piece at least it suggests that the problem is not electrical. The question is the following, for the motorcycle model it carries 25 and 240 jets. Could it be a limitation intentionally that the bike is rich in highs so as not to deliver all the power and maybe it really would take 210? It is even strange that with the reed switch plugged in its original place it has made that speed or perhaps having the 3rm20 cdi such limitation does not work. What do you think about the jet? Have you read something similar? I never understood why some models have the same top end kit, exhaust and carburetor, but they still have different jets. Sorry if I wrote too much, I was excited to see a beam of light in the problem.

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        • M MadGyver
          27 Feb 2025, 14:00

          Is the power valve correctly aligned,if it has the diamond shaped base?

          F Offline
          F Offline
          facundo duarte
          wrote on 27 Feb 2025, 16:50 last edited by facundo duarte
          #8

          c@MadGyver Thanks for writing friend, it is the rectangular version where the pulley fits, it is well aligned and works correctly, at least as far as the pv is concerned.

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          • F Offline
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            facundo duarte
            wrote on 27 Feb 2025, 17:24 last edited by
            #9

            On my previous two-stroke, once the stator ignition coil went bad, when I installed a new but inferior one, the bike felt rich at high revs, so it tolerated/needed less fuel than before to run properly, although it translates to less power if the bike tolerates less gas. Something similar may be happening, although on this bike everything looks so healthy and with little use that I doubt it but I will have to check it again, maybe a ground cable? Sorry friends again for so much text and thank you for your time.

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            • R Offline
              R Offline
              Rallyfinnen
              wrote on 27 Feb 2025, 17:24 last edited by
              #10

              Sounds like you disconnected the boost bottle on the intake? (YEIS i think Yamaha calls it)
              Did you plug the hole? If so, it should not idle, but would run significantly leaner on WOT, giving more rpm if it was rich before.

              F 1 Reply Last reply 27 Feb 2025, 17:44
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              • R Offline
                R Offline
                Rallyfinnen
                wrote on 27 Feb 2025, 17:26 last edited by
                #11

                I mean if you did not plug the hole.
                If you remove it and just plug the hole, it should not affect full throttle at all.

                F 1 Reply Last reply 27 Feb 2025, 17:59
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                • R Rallyfinnen
                  27 Feb 2025, 17:24

                  Sounds like you disconnected the boost bottle on the intake? (YEIS i think Yamaha calls it)
                  Did you plug the hole? If so, it should not idle, but would run significantly leaner on WOT, giving more rpm if it was rich before.

                  F Offline
                  F Offline
                  facundo duarte
                  wrote on 27 Feb 2025, 17:44 last edited by
                  #12

                  @Rallyfinnen Hello friend, it is not the yeis that disconnected. What I disconnected is a black bottle that goes on the side of the frame and is screwed into it. It connects to the rubber that joins the air filter box to the carburetor, I understand that not all models have it.

                  1 Reply Last reply
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                  • R Rallyfinnen
                    27 Feb 2025, 17:26

                    I mean if you did not plug the hole.
                    If you remove it and just plug the hole, it should not affect full throttle at all.

                    F Offline
                    F Offline
                    facundo duarte
                    wrote on 27 Feb 2025, 17:59 last edited by
                    #13

                    @Rallyfinnen Continuing with what was said, by giving it more air in this way the bike improved significantly. That's why I doubt and maybe a 210 plane is needed instead of 240. Maybe this is some kind of limitation? What really changes in the previous, more similar models to carry this model with larger aircraft? Or I have a weak spark at high rpm, so with a higher, leaner air ratio, the mixture reaches the rpm it should reach but probably with less power.

                    S 1 Reply Last reply 27 Feb 2025, 18:13
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                    • F facundo duarte
                      27 Feb 2025, 17:59

                      @Rallyfinnen Continuing with what was said, by giving it more air in this way the bike improved significantly. That's why I doubt and maybe a 210 plane is needed instead of 240. Maybe this is some kind of limitation? What really changes in the previous, more similar models to carry this model with larger aircraft? Or I have a weak spark at high rpm, so with a higher, leaner air ratio, the mixture reaches the rpm it should reach but probably with less power.

                      S Offline
                      S Offline
                      SpookDog
                      wrote on 27 Feb 2025, 18:13 last edited by
                      #14

                      @facundo-duarte

                      Try cleaning your air filter. All you are doing is by-passing the filter and sponge element.

                      1 Reply Last reply
                      1
                      • C Offline
                        C Offline
                        Calum
                        wrote on 27 Feb 2025, 19:04 last edited by
                        #15

                        Go with what @SpookDog said. If you removed the YEIS from the Carb Boot...your carb settings should be okay (perhaps a little lean), since you're not altering the air after the carburettor, merely increasing flow over the carb. If you remove the one on the inlet manifold then yes it'll be a huge air leak, but you didn't....

                        So that to me sounds like poor flow through the airbox system. So remove the airbox lid and give it a good clean. Make sure the snorkel isn't obstructed etc.

                        Always Originate, Never Pirate!

                        S 1 Reply Last reply 27 Feb 2025, 19:55
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                        • C Calum
                          27 Feb 2025, 19:04

                          Go with what @SpookDog said. If you removed the YEIS from the Carb Boot...your carb settings should be okay (perhaps a little lean), since you're not altering the air after the carburettor, merely increasing flow over the carb. If you remove the one on the inlet manifold then yes it'll be a huge air leak, but you didn't....

                          So that to me sounds like poor flow through the airbox system. So remove the airbox lid and give it a good clean. Make sure the snorkel isn't obstructed etc.

                          S Offline
                          S Offline
                          SpookDog
                          wrote on 27 Feb 2025, 19:55 last edited by SpookDog
                          #16

                          @Calum

                          yeah, yamaha doesnt recomend cleaning the foam element with petrol, but as long as you dry it out its noy a problem. then lightly oil the foam and sqeeze out any excess in a bit or two of kitchen roll. make sure to clean the rubber 'snorkel' and any dirt/dust from the top of the airbox...
                          brake clutch cleaner works well too...

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                          • F Offline
                            F Offline
                            facundo duarte
                            wrote on 27 Feb 2025, 20:24 last edited by
                            #17

                            @SpookDog @Calum Thanks again for the suggestions but let's go in parts, Jack said, I made sure the air filter was clean, then maybe I expressed myself wrong or it was the translator's fault, but I repeat, I didn't remove the yeis. I removed the black bottle that is bolted to the frame on the side and fits into the rubber that connects the air filter housing to the carburetor. That is, imagine the air entering in excess when opening that inlet and very little through the air filter box. The logical thing would be to think that it would work worse but it was when the bike worked better at least in wot and it did not have the damn failure despite the large excessive air intake, which makes me think that perhaps I still have an electrical fault that I have not yet detected and that would make a weak spark at high revolutions that is not powerful enough to burn the fuel in wot. I even tried with everything connected without the snorkel and although it improved it was still a little rich so imagine.

                            C 1 Reply Last reply 27 Feb 2025, 21:28
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                            • F facundo duarte
                              27 Feb 2025, 20:24

                              @SpookDog @Calum Thanks again for the suggestions but let's go in parts, Jack said, I made sure the air filter was clean, then maybe I expressed myself wrong or it was the translator's fault, but I repeat, I didn't remove the yeis. I removed the black bottle that is bolted to the frame on the side and fits into the rubber that connects the air filter housing to the carburetor. That is, imagine the air entering in excess when opening that inlet and very little through the air filter box. The logical thing would be to think that it would work worse but it was when the bike worked better at least in wot and it did not have the damn failure despite the large excessive air intake, which makes me think that perhaps I still have an electrical fault that I have not yet detected and that would make a weak spark at high revolutions that is not powerful enough to burn the fuel in wot. I even tried with everything connected without the snorkel and although it improved it was still a little rich so imagine.

                              C Offline
                              C Offline
                              Calum
                              wrote on 27 Feb 2025, 21:28 last edited by
                              #18

                              @facundo-duarte Yes that's correct.

                              On later models Yamaha fitted two YEIS bottles.

                              One to the inlet manifold, and then one to the carburetor boot. You've removed the one fitted to the carburetor boot.

                              It sounds like not enough air flow to me.

                              If you remove the air filter/carburetor boot altogether you can see if your problem goes away and that tells you it's the airbox.

                              Always Originate, Never Pirate!

                              1 Reply Last reply
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                              • F Offline
                                F Offline
                                facundo duarte
                                wrote on 27 Feb 2025, 21:49 last edited by
                                #19

                                @Calum Oh well, I didn't know he also had the same name as the other one, good to know. On the other hand, if the motorcycle is original and not modified, why do you suggest that the problem could be in the airbox if it is in good condition? Or did I misunderstand what you mean?

                                1 Reply Last reply
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                                • C Offline
                                  C Offline
                                  Calum
                                  wrote on 27 Feb 2025, 21:51 last edited by
                                  #20

                                  Do you have the Snorkel fitted? Is there anything obstructing the top of the airbox?

                                  I think this based off what you've told me. Sounds like giving it more air has resulted in night and day performance. Ergo, it's intake related.

                                  Always Originate, Never Pirate!

                                  F 1 Reply Last reply 27 Feb 2025, 22:04
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                                  • C Calum
                                    27 Feb 2025, 21:51

                                    Do you have the Snorkel fitted? Is there anything obstructing the top of the airbox?

                                    I think this based off what you've told me. Sounds like giving it more air has resulted in night and day performance. Ergo, it's intake related.

                                    F Offline
                                    F Offline
                                    facundo duarte
                                    wrote on 27 Feb 2025, 22:04 last edited by
                                    #21

                                    @Calum That's right, I already tried with and without a snorkel. without it works better in wot, although it still needed a little more, that's why I tried removing the yeis that is screwed to the frame. If we look at the problem with the naked eye it would suggest that I have a main jet that is too rich, however I checked its sizes including the pilot and they are fine, they correspond to the DTR model.

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                                    • F Offline
                                      F Offline
                                      facundo duarte
                                      wrote on 27 Feb 2025, 22:15 last edited by facundo duarte
                                      #22

                                      @Calum Now that I look at it I don't know if it has anything to do with it, but I have a four-wire connector disconnected near the water tank in the back, apart from the one for the lights and indicators. I read that it is for the neutral relay but it doesn't have it, I have to attach a cable or something. Could it have something to do with that?

                                      1 Reply Last reply
                                      -1
                                      • C Offline
                                        C Offline
                                        Calum
                                        wrote on 27 Feb 2025, 22:17 last edited by
                                        #23

                                        I'd leave the jetting alone, Yamaha spent a lot of R&D in the jetting.

                                        You should be running the bike with the snorkel in as it's adverse to performance to remove it.

                                        Make sure that the carb boot is clear of any debris.

                                        Always Originate, Never Pirate!

                                        1 Reply Last reply
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                                        • F Offline
                                          F Offline
                                          facundo duarte
                                          wrote on 27 Feb 2025, 22:43 last edited by facundo duarte
                                          #24

                                          I agree @Calum , I will let you know if there is any news. Did you see the message above about the neutral relay?

                                          S 1 Reply Last reply 5 Mar 2025, 15:05
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