tach signal wire NGC

[Chuck in Indiana]

Cross posted from the MZ list..

Well, they said it could't be done, so I tackled it with a grin.


I couldn't do it either.  ;D
Took the rattling tach apart, and a little gizmo (technical term) fell out. You could see where it had originally been soldered to the pc board and had a broken leg. Thought "aha" this will be an easy fix. Had Dorcia come out and help me solder it back on the board.. she's a whiz. Used to repair electonics, yada yada, but she didn't know what the gizmo was, either. At any rate, checked continuity after putting it back, looks good, glued it down with a hot melt gun so it wouldn't vibrate off again. Plugged it in, and.... nothin.   ??? I really did think it would work.
So. Anyone have a spare tach?
I've found the tach signal wire. How do I test it to make no shit sure that I have a tach signal?

[Semper-guzzi]

Which bike is it off of?

[Morizzi]

Hi Chuck,

Tacho signals are usually off one of the coils. When the points (or their electronic equal) open then the current stops flowing through the points and goes to the tacho.

Ignition on, voltmeter to the signal line then rotate the engine. You should see a reading after a couple of rotations.

Cheers

Rod

[Chuck in Indiana]

Which bike is it off of?

95 Skorpion tour.

[Chuck in Indiana]

Hi Chuck,

Tacho signals are usually off one of the coils. When the points (or their electronic equal) open then the current stops flowing through the points and goes to the tacho.

Ignition on, voltmeter to the signal line then rotate the engine. You should see a reading after a couple of rotations.

Cheers

Rod

Ok, thanks, Rod.  ;-T

[Chuck in Indiana]

Hmm, a guy on the MZ forum said

find a ham radio operator with an oscilloscope ..
that actually knows how to use it to look at it through a capacitor
for the pulses

that's above my pay grade. Necessary?

[charlie b]

Do you have a meter that reads frequency?  It should work.

If you just want to see if there is something there, try an AC volt meter.  It won't read the correct value, but, it should give you something.

[Chuck in Indiana]

Do you have a meter that reads frequency?  It should work.

If you just want to see if there is something there, try an AC volt meter.  It won't read the correct value, but, it should give you something.

Thanks. I'll put it on AC and give it a try. Needless to say, I'm out of my league.. ;D

[Morizzi]

Chuck,

Not sure AC will work but if it does then good but the current only goes one way.

As i stated previously if the wire comes from the coil, not the ecu, then when the points are closed the power goes through the coils, some will still go to the tach though. Not sure what that voltage will be but it will be less than the full battery voltage due to feeding the coils too. When the points open the full voltage goes to the tach.

With a standard voltmeter/multimeter you are looking for change. If you have a spare electronic tach then just hook that up.Doesn't matter if its for a car or plane, 4,6 or 8 cyl. If you get a reading then its not the tach wire.

Rod

[charlie b]

Yeah, it depends on the meter and how it measures AC.

Might even try just measuring using the DC volt scale too.  You're just looking for something.

[Chuck in Indiana]

Chuck,

Not sure AC will work but if it does then good but the current only goes one way.

As i stated previously if the wire comes from the coil, not the ecu, then when the points are closed the power goes through the coils, some will still go to the tach though. Not sure what that voltage will be but it will be less than the full battery voltage due to feeding the coils too. When the points open the full voltage goes to the tach.

With a standard voltmeter/multimeter you are looking for change. If you have a spare electronic tach then just hook that up.Doesn't matter if its for a car or plane, 4,6 or 8 cyl. If you get a reading then its not the tach wire.

Rod

The signal comes out of the Yamaha magic box, whatever it is.  ;D There are three wires that go to the tach.. ground, positive,and signal. As long as I can't let the smoke out, I'll give it a try.

[charlie b]

With all this low voltage stuff it is sometimes nice to have a logic probe.  Tells you if there is a signal, if it is pos or neg and some have an indicator for a pulsed signal.