White LEDs for Neutral and Turn Signal indicator lights

[Easy Rider]

Originally Posted by 5th_bike

Ooh, I realize now that when it makes 1,400 rpm, it fires only 700 times per minute (two revolutions per ignition, it's a "4-stroke" after all...) therefore there are 11 to 12 'explosions' per second, that sounds about right. You only hear 700 beats yet it does run 1,400 rpm.

That is true but consider this: I "think" I remember that this is a "double fire" arrangement, in that the spark plug actually fires every revolution (yes, at the top of the exhaust stroke too) because it is simpler to design that way and the extra spark is just wasted.

If that is true and the tach is set wrong, it would be counting each spark as a rev. and indicating TWICE the actual RPM.

I'm not necessarily saying that yours is doing that, since the rpm/gear/speed readings seem to come out right when going down the road; just something to keep in mind for future discussions !!

(And I won't mention how idling too slow is somewhat like lugging the engine.....until I'm able to get some readings on mine !!)

[5th_bike]

Wel if it sparks every revolution but only explodes every other revolution, and it counts a spark as one revolution, then it will indicate the right rpm. What I meant to say was "you only HEAR half the rpms".
This tach is constructed for Harleys, and I know that they spark every revolution. I think they actually spark only once every rev for both cylinders, such that the front cylinder gets its spark early (it does most of the work) and the rear cylinder gets its spark late (so it won't run hot).

[Easy Rider]

Originally Posted by 5th_bike

Wel if it sparks every revolution but only explodes every other revolution, and it counts a spark as one revolution, then it will indicate the right rpm.

That's true. I said "if the tach isn't set right". Some have switches to change from "spark only on power stroke" (single fire) to "spark every revolution" (double fire). If the tach is set for single fire on a double fire machine, it will read 2X the real RPM.