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What hertz from coil to tachometer

Discussion in 'XJ Technical Chat' started by Aussie, May 10, 2022.

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  1. Aussie

    Aussie New Member

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    Hi, I have a 1982 Maxim 650 and the tach is dead. I am getting it rebuilt, the question I was asked is what is the hertz at idle (1260 rpm) so the mechanic can set it during the rebuild?
     
    Aussie, May 10, 2022
    #1
  2. SQLGuy

    SQLGuy Well-Known Member

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    Since it's wasted spark, the coil fires once per rotation of the crank. So, 1260 / 60 seconds per minute = 21 Hz.
     
    SQLGuy, May 10, 2022
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  3. Aussie

    Aussie New Member

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    Thank you for the quick reply. Life saver. Cheers, Mate!
     
    Aussie, May 10, 2022
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  4. Aussie

    Aussie New Member

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    Because there are two coils does this mean you have to double the hrtz for the tach?
     
    Aussie, May 31, 2022
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  5. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    No. The tachometer only receives signal from one coil.
     
    k-moe, Jun 1, 2022
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  6. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Out of curiosity, who is repairing your tach?
     
    chacal, Jun 1, 2022
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    k-moe likes this.
  7. Aussie

    Aussie New Member

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    Cheers. The company is Humphrey Instruments in Unanderra, NSW
     
    Aussie, Jun 2, 2022
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  8. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Thank you for the info. Can you give us a little more info as to what they are replacing, or are they building a new circuit board for it, or ?????
     
    chacal, Jun 2, 2022
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  9. Aussie

    Aussie New Member

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    He built a new circuit board and calibrated it to the RPM and hrtz. Quick turn around 3 days. I should get it back on Monday.
     
    Aussie, Jun 2, 2022
    #9
  10. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Please let us know how it looks and performs!
     
    chacal, Jun 2, 2022
    #10

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