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  1. #1
    carbuff91's Avatar
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    Quick question on a ENMCO PT141 Tach.

    Hi all,

    I installed the tach today and wanted to know the general idle that the GP1200R likes to idle at? This tach has three setting....
    1. Fires twice per revolution
    2. Fires once per revolution
    3. Fires every other revolution

    I'm thinking that our boats the Number 2 fires once per revolution...correct? I looks like my idle is around 2,000 or a little more rpm's though...is that about right? Thanks for any input...here's a link to the tach.

    Steve

    http://enmco.thomasnet.com/viewitems...nce-hour-meter


  2. #2
    Moderator RX951's Avatar
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    Two-Stroke engines fire once every revolution.
    Four-Stroke engines fire every other revolution.

    My 12R idles at 1400 rpm +/- 50

  3. #3
    carbuff91's Avatar
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    Thanks,

    It's pickup wire is suppose to wrap around the first plug wire too, right? The cylinder that is closest to the handlebars. I assume that is correct.

    Thanks again

  4. #4
    Moderator RX951's Avatar
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    Yes. I don't think it matters too much.

    But, when I had my tiny-tach (similar), I wrapped the first wire 5-6 times.

    Make sure the wire is clean and free of any residue/oil/silicone.

    Make sure the Grounding Wire is secured well.

  5. #5
    the info is almost ok
    actually the gpr fire ones per revolution
    a 2 cylinder 2 stroke will fire 2 times per revolution except 951 99 and up
    a fx 140 will fire one time per revolution and a HO and vx110 1 every other rev
    jut kept these in mind

  6. #6
    Moderator RX951's Avatar
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    Thank for you input Bill.

    Are CDI's on the Yamaha GPRs different on their firing sequence from other two strokes ?

    Because from what I have always remembered and due to the cycle of 2 & 4 strokes, I don't remember anything different.


    Using this as reference also, it also confirms that 2 strokes fire 1once per rev, and 4 strokes every other......unless the GPR is different form other two strokes ??


    Just digging more info from ya bud.......

    Just asking so I can learn more if there is something I need to know for future reference.

    Your input is highly valued !



    http://science.howstuffworks.com/two-stroke1.htm

  7. #7
    the deferens is that 99% of 2 cylinders share the coil (these is call Siamese coils )2 spark wires and 2 trigger wires so these coil fire even wen the piston is down on the gpr or in 3 cylinders each have one coil since you cant fire wen the piston is in the middle position and these will happen in all 3 cylinders motors
    on the 4 stroke like the fx 140 they share coils again and 2 cylinders will fire at the same time but only one will have the valves close (power stroke)the other will be on the dead stroke
    on the HO and vx110 they use independent coils for every cylinder these work the same way us the 140 but will be spark only on the power stroke

  8. #8
    Moderator RX951's Avatar
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    Thanks Bill.

    Then the perfect two-stroke firing theory will only apply if each cylinder had their own coil, then firing would only be needed at the recommended revolution.....

    good example; lawn mower (1 cyl)

    Makes sense. I didn't even snap to that fact of coil sharing taking place.

    Thanks for explaining that.

  9. #9
    carbuff91's Avatar
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    So,
    What's a good tach to use other then a tiny? I had seen where it says that the Advent CDI has a digital tach output...where is that at on the CDI?

  10. #10
    Moderator RX951's Avatar
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    Pet-2100 or Pet-2500

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