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Connecting a Tachometer For Carb Tuning

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  • #1

    Connecting a Tachometer For Carb Tuning

    Hello Folks,
    Recently I read a very nicely written Do it Yourself guide on Tuning your Carburetor for Optimal performance and fuel efficiency. I followed the given instructions and and got very rewarding results. The only slack was that I totally relied on the sound of the vehicle where as using a tachometer was a better and easy option. The problem was that I didn't had a tachometer.
    Fortunately Today I managed managed to get a RPM meter one fitted in Older Bajaj Bikes. Now I where do I connect it. It has three wires

    Brown

    Black Yellow


    Blue

    I am attaching a model wiring diagram. (just for block reference and get a basic idea)

    At what point(s) are the wires are to be connected.

    (I wish to connect the tachometer, for tuning purpose, to my LML Vespa Spl., Hero Honda Super Splendor & Kinetic Nova 135)

    Thanks & Regards.
    Last edited by zmint; 11-07-2009, 12:01 PM.
    A Bird in the Bush is Worth, 2 in the Hand, cause
    Pleasure lies in Pursuit, not in Possession
    Tags: None
  • #2
    Query Approved.
    :)

    Comment

    • #3
      Tacho are of 2 types. One is impulse type tacho which is used with a CDI equipped bike. They need higher voltage signal to operate (around 100V) The other one is the normal tacho which operates on TCI equipped bikes. They operate using 12V signals.

      Now, as for the connections, the signal wire goes to ignition coil +ve.
      Your biking tells a lot about the person you are!

      Comment

      • #4
        Originally posted by abhijeet080808 View Post
        impulse type tacho is used with a CDI equipped bike.
        I think bajaj pulsar is a CDI equipped bike. (I got the tacho from one of these bikes)

        They need higher voltage signal to operate (around 100V)
        You mean the PULSE signal(BLUE WIRE) should get around 100v DC.

        Now, as for the connections, the signal wire goes to ignition coil +ve.
        but on the Coil positive input, I think it is 12V ?
        any how I tried connecting :
        brown = Battery +ve
        black yellow = Battery -ve
        blue = cdi OUT to ignition coil IN i.e. +ive of Coil.

        But nothing happened..
        Please Help ...
        A Bird in the Bush is Worth, 2 in the Hand, cause
        Pleasure lies in Pursuit, not in Possession

        Comment

        • #5
          Yes, Pulse wire should get the 100V+. Which bike have you tried it on? If that bike does not have CDI, it would not work.
          Your biking tells a lot about the person you are!

          Comment

          • #6
            Originally posted by abhijeet080808 View Post
            Which bike have you tried it on?
            Actually I tried it on My Kinetic Nova 135 & LML NV SPL (Self Start).

            If that bike does not have CDI, it would not work.
            I guess both of these have a CDI Unit. (That is atleast what their circuit states) & I have myself located their presence.
            A Bird in the Bush is Worth, 2 in the Hand, cause
            Pleasure lies in Pursuit, not in Possession

            Comment

            • #7
              In that case recheck the wiring. Blue to Ignition coil +ve. If it still does not work, I guess, it may be caused by some voltage differences between Pulsar CDI and KiHo CDI.
              Your biking tells a lot about the person you are!

              Comment

              • #8
                Whatever it may be, there should a transducer to measure the speed at the engine end, have you checked whether anything of that kind is available. This transducer sends the signal to the CDI or other ECU to monitor speed.

                I think, it is possible to use a mechanical tachometer for idle speed setting.

                Comment

                • #9
                  Originally posted by bala_racing View Post
                  Whatever it may be, there should a transducer to measure the speed at the engine end, have you checked whether anything of that kind is available. This transducer sends the signal to the CDI or other ECU to monitor speed.

                  I think, it is possible to use a mechanical tachometer for idle speed setting.
                  The transducer (actually trigger coil) signal is for the CDI. Tacho can not read this directly.

                  A mechanical tacho uses the same system as speedometer right? So how would you connect this? Have you done anything like this?
                  Your biking tells a lot about the person you are!

                  Comment

                  • #10
                    Originally posted by abhijeet080808 View Post
                    The transducer (actually trigger coil) signal is for the CDI. Tacho can not read this directly.

                    A mechanical tacho uses the same system as speedometer right? So how would you connect this? Have you done anything like this?
                    The mechanical tacho I'm talking about is of the contact type , it has a shaft which we need to press against the cranshaft end. It reads the speed. Analog/digital display is available withit. It will not appear as a tachometer connected to commercial bikes.

                    I've used this in my college to set the idle speed of a scooter engine in our automobile lab.

                    Comment

                    • #11
                      Originally posted by abhijeet080808 View Post
                      In that case recheck the wiring. Blue to Ignition coil +ve.
                      I suppose Ignition coil +ve is the one coming from CDI and going into the Coil. Right ? it the not the one coming out of Ig. Coil to the spark plug ???

                      If it still does not work, I guess, it may be caused by some voltage differences between Pulsar CDI and KiHo CDI.
                      I the forum I read somewhere that pulsar has two spark plugs.
                      In respect to this do I have to consider something like THIS link Tachometer Installation states
                      regarding
                      Single Fire Adapter
                      The problem: the majority of motorcycle tachometers are designed to work with dual fire ignitions.
                      The solution: A dual fire adapter that takes pulses from both coils and feeds them to the tach.


                      A Bird in the Bush is Worth, 2 in the Hand, cause
                      Pleasure lies in Pursuit, not in Possession

                      Comment

                      • #12
                        No, the tacho is connected to only one of the 2 ignition coils. So, it works the same way. And yeah, the wire from CDI to Ign coil is the one.
                        Your biking tells a lot about the person you are!

                        Comment

                        • #13
                          I doubt the meter. Is there a way I can check it ?
                          Negative Postive is OK (12 V DC).
                          Can I feed some sort of DC current to the pulse wire in order to check it.
                          A Bird in the Bush is Worth, 2 in the Hand, cause
                          Pleasure lies in Pursuit, not in Possession

                          Comment

                          • #14
                            Connect it to the pulse wire from another Pulsar and see.
                            Your biking tells a lot about the person you are!

                            Comment

                            • #15
                              Originally posted by abhijeet080808 View Post
                              Connect it to the pulse wire from another Pulsar and see.
                              As per Pulsar Diag Blue wire goes to Ht coil +ve, Brown batt +ve and black yellow to -ve

                              Check the tacho with other Pulsar as Abhi said.
                              Do it Yourself, what so ever, if Possible
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