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Thread: TZR/TDR tacho

  1. #1
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    Default TZR/TDR tacho

    does a TDR tacho work on a TZR - i know they have different CDI's so not sure



    Tony

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    Default Re: TZR/TDR tacho

    There are two ways of driving the tacho from the CDI.

    One is with one of the leads that go to the coil, the other is with the wire that goes to the power valve controller. Either way, you are giving the tacho a short high voltage pulse at the firing rate.



    So AFAIUI, and there may be someone out there who will correct me, you can drive the wrong tacho from the right CDI but you have to wire it up slightly differently.



    Incidentally, the pulse that the CDI sends out is enormous - hundreds of volts, but the tacho only needs about a 10 V pulse to work. So the CDI is sending pulses round the wiring that are beyond the rating of the connectors and cable that many people use. It potentially creates huge problems for both reliability and for EMC.



    Nick


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    Default Re: TZR/TDR tacho

    Tony



    Looking at the wiring diagrams for both bikes, they are wired up the same way, both bikes run on wasted spark systems so the pulse count is the same, the tachometer part numbers are the same except for the 3 digit prefix, so I'd guess that for all intents and purposes they are interchangeable in a hovercraft application. I found to my cost that the later TZR 3XV tacho isnt compatible - it reads at half speed!



    Kevin

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