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DT125R FORUM

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  4. When to re-jet

When to re-jet

Scheduled Pinned Locked Moved Carburetor
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  • DTleeD Offline
    DTleeD Offline
    DTlee
    wrote on last edited by
    #1

    After fitting a full depp system and turning the power valve so it’s working as it should, should I be re-jetting the carb if so what did you find works best? Currently it cuts back at top end after 6000rpm. I’m just wondering if this has something to do with it??

    S 1 Reply Last reply
    0
    • declanD Offline
      declanD Offline
      declan
      wrote on last edited by
      #2

      @dtlee are you positive you set the powervalve up right? Pv kicks in around 6 so if it's not working correctly you will know about it

      S 1 Reply Last reply
      1
      • declanD declan

        @dtlee are you positive you set the powervalve up right? Pv kicks in around 6 so if it's not working correctly you will know about it

        S Offline
        S Offline
        SpookDog
        wrote on last edited by
        #3

        @declan

        “ “
        My thoughts exactly.

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        • DTleeD DTlee

          After fitting a full depp system and turning the power valve so it’s working as it should, should I be re-jetting the carb if so what did you find works best? Currently it cuts back at top end after 6000rpm. I’m just wondering if this has something to do with it??

          S Offline
          S Offline
          SpookDog
          wrote on last edited by
          #4

          @dtlee

          Have you pinned the power valve or is it servo operated?

          1 Reply Last reply
          0
          • DTleeD Offline
            DTleeD Offline
            DTlee
            wrote on last edited by
            #5

            i turned the powervalve quite a long time ago so it was flush with the port and it ran fine with plenty of power for 5 or 6 long rides after that so I'm guessing that's set fine? it just recently its starting cutting back around 6000rpm and really spluttering. i haven't messed with any jetting on it thats all complete standard still. i did notice the spark plug was slightly black with a bit of wet oil but that's about it. is it worth just putting a spark plug on that burns hotter? current one is a BR9ES

            i got the bike completely standard as a french import with 8000k on the clock. i put a full depp system on it, have turned the powervalve so its flush and moved the reed switch nothing else has been touched.

            CalumC 1 Reply Last reply
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            • DTleeD DTlee

              i turned the powervalve quite a long time ago so it was flush with the port and it ran fine with plenty of power for 5 or 6 long rides after that so I'm guessing that's set fine? it just recently its starting cutting back around 6000rpm and really spluttering. i haven't messed with any jetting on it thats all complete standard still. i did notice the spark plug was slightly black with a bit of wet oil but that's about it. is it worth just putting a spark plug on that burns hotter? current one is a BR9ES

              i got the bike completely standard as a french import with 8000k on the clock. i put a full depp system on it, have turned the powervalve so its flush and moved the reed switch nothing else has been touched.

              CalumC Offline
              CalumC Offline
              Calum
              wrote on last edited by
              #6

              @dtlee Depends what you mean by "turned the powervalve flush with the port".

              The powervalve needs to be setup appropriately, not just abitrarily moved, unless pinned. To see if it's the PV I usually just pin the valve in the open position and disconnect the servo. If it's running sweet past 6K after then you know that you've messed the PV settings.

              If not, then you know the problem lies elsewhere.

              Is it jetting? Unlikely, the bikes default jetting is spot on.

              Always Originate, Never Pirate!

              DTleeD 2 Replies Last reply
              0
              • CalumC Calum

                @dtlee Depends what you mean by "turned the powervalve flush with the port".

                The powervalve needs to be setup appropriately, not just abitrarily moved, unless pinned. To see if it's the PV I usually just pin the valve in the open position and disconnect the servo. If it's running sweet past 6K after then you know that you've messed the PV settings.

                If not, then you know the problem lies elsewhere.

                Is it jetting? Unlikely, the bikes default jetting is spot on.

                DTleeD Offline
                DTleeD Offline
                DTlee
                wrote on last edited by
                #7

                @calum cheers ill give that a try first, see if i can rule one thing out at a time. i want to mess with as little as possible as my mechanical knowledge is near nothing, although i di like to try and understand how it all works and learn for future.

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                • CalumC Calum

                  @dtlee Depends what you mean by "turned the powervalve flush with the port".

                  The powervalve needs to be setup appropriately, not just abitrarily moved, unless pinned. To see if it's the PV I usually just pin the valve in the open position and disconnect the servo. If it's running sweet past 6K after then you know that you've messed the PV settings.

                  If not, then you know the problem lies elsewhere.

                  Is it jetting? Unlikely, the bikes default jetting is spot on.

                  DTleeD Offline
                  DTleeD Offline
                  DTlee
                  wrote on last edited by
                  #8

                  @calum what is the easiest way to temporarily pin the powervalve open to test this ?

                  CalumC S 2 Replies Last reply
                  0
                  • DTleeD DTlee

                    @calum what is the easiest way to temporarily pin the powervalve open to test this ?

                    CalumC Offline
                    CalumC Offline
                    Calum
                    wrote on last edited by
                    #9

                    @dtlee Take the exhaust off, turn the ignition on and the powervalve should automatically go to its most open position. If it's not, then you'll need to adjust the cables and switch the ignition on and off to reset the valve. Repeat until the valve is completely flush with the exhaust port. Then disconnect the connector block that powers the valve.

                    Always Originate, Never Pirate!

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                    • DTleeD DTlee

                      @calum what is the easiest way to temporarily pin the powervalve open to test this ?

                      S Offline
                      S Offline
                      SpookDog
                      wrote on last edited by
                      #10

                      @dtlee

                      Don’t change the plug temp. Find out and fix the fault. Check your filter isn’t blocked. Black and wet indicates rich running, not burning all the mixture. Make sure the choke is closing properly. Rule out these then if not fixed check ignition...

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                      • DTleeD Offline
                        DTleeD Offline
                        DTlee
                        wrote on last edited by
                        #11

                        Thanks for the reply’s, I’ll pin open the powervalve and check that and while I’m there I’ll take the carb out and give it a clean as it’s not been taken off in the two years I’ve had it, the bike doesn’t get a great deal of use. It has a new air filter in it so that should eliminate that being a problem.

                        markus.wM S 2 Replies Last reply
                        0
                        • DTleeD DTlee

                          Thanks for the reply’s, I’ll pin open the powervalve and check that and while I’m there I’ll take the carb out and give it a clean as it’s not been taken off in the two years I’ve had it, the bike doesn’t get a great deal of use. It has a new air filter in it so that should eliminate that being a problem.

                          markus.wM Offline
                          markus.wM Offline
                          markus.w
                          wrote on last edited by
                          #12

                          @dtlee the bike doesn’t get a great deal of use? Maybe that's your problem as it can only take a few weeks for the fuel in the carb to gum up and cause a partial blockage and even more so if you premix. maybe you just need to give all the jets a good clean. If you know it won't be used for a while it's good practice to turn off fuel tap whilst still running and let it run out of fuel so the carb is empty.

                          DTleeD 1 Reply Last reply
                          0
                          • DTleeD DTlee

                            Thanks for the reply’s, I’ll pin open the powervalve and check that and while I’m there I’ll take the carb out and give it a clean as it’s not been taken off in the two years I’ve had it, the bike doesn’t get a great deal of use. It has a new air filter in it so that should eliminate that being a problem.

                            S Offline
                            S Offline
                            SpookDog
                            wrote on last edited by
                            #13

                            @dtlee
                            Why pin it? Do you not have a power servo for the power valve?

                            Electrical misfire can cause a black wet plug as well...

                            CalumC 1 Reply Last reply
                            0
                            • S SpookDog

                              @dtlee
                              Why pin it? Do you not have a power servo for the power valve?

                              Electrical misfire can cause a black wet plug as well...

                              CalumC Offline
                              CalumC Offline
                              Calum
                              wrote on last edited by Calum
                              #14

                              @spookdog Pinning it open rules out the powervalve which is what I see 90% of the time being the problem. I suspect, by the way they've stated they've "changed" the valve settings that this is the cause.

                              Always Originate, Never Pirate!

                              1 Reply Last reply
                              0
                              • markus.wM markus.w

                                @dtlee the bike doesn’t get a great deal of use? Maybe that's your problem as it can only take a few weeks for the fuel in the carb to gum up and cause a partial blockage and even more so if you premix. maybe you just need to give all the jets a good clean. If you know it won't be used for a while it's good practice to turn off fuel tap whilst still running and let it run out of fuel so the carb is empty.

                                DTleeD Offline
                                DTleeD Offline
                                DTlee
                                wrote on last edited by
                                #15

                                @markus-w good shout, i use it every couple of months so ill give that a try as well.

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