Tachometer not working - 1983 KZ1000J3

1983 KZ1000J3
Problem: Tachometer do not work.

Tachometer is fed with three wires:
1) Black/Yellow (ground)
2) Brown (switched battery voltage)
3) Black (Ignition coil signal)

Ground is OK and brown wire shows battery voltage when ignition key is "on".
About ignition coil signal, both my KZ750 and 1981/1982 KZ1000/1100 (*see note 1) manuals states this wire should read 2-4 volts when engine is running. Problem is that I measure battery voltage when key is "on", whatever the engine is running or not. I measured both coils and got the same result.

Anyone has a clue about what is wrong please?

* Note 1: Not sure if this is the right procedure to use for 1983 1000J3 but a tachometer is a tachometer so I think it should work the same.

Note 2: For those not aware, J3 instruments are not individual but grouped into a cluster. Should be the same as 1983 ELR.

Note 3: What is really strange is that tachometer sometimes work… Not immediately at engine start up but, sometimes, after I rev the engine at around 3-5000, the needle start to move and from then, seem to correctly shows the engine RPMs…

Thanks!

wrote:

1983 KZ1000J3
Problem: Tachometer do not work.

Tachometer is fed with three wires:
1) Black/Yellow (ground)
2) Brown (switched battery voltage)
3) Black (Ignition coil signal)

Ground is OK and brown wire shows battery voltage when ignition key is "on".
About ignition coil signal, both my KZ750 and 1981/1982 KZ1000/1100 (*see note 1) manuals states this wire should read 2-4 volts when engine is running. Problem is that I measure battery voltage when key is "on", whatever the engine is running or not. I measured both coils and got the same result.

Anyone has a clue about what is wrong please?

* Note 1: Not sure if this is the right procedure to use for 1983 1000J3 but a tachometer is a tachometer so I think it should work the same.

Note 2: For those not aware, J3 instruments are not individual but grouped into a cluster. Should be the same as 1983 ELR.

Note 3: What is really strange is that tachometer sometimes work… Not immediately at engine start up but, sometimes, after I rev the engine at around 3-5000, the needle start to move and from then, seem to correctly shows the engine RPMs…

Thanks!

Do you have a wiring diagram for it Claude, I assume it takes the trigger signal from the igniter ? If the trigger pulse is ground (which it sounds like since the unit has an ign live) and is showing full voltage that would suggest an "open circuit" between the test point and the igniter or an intermittent fault in the igniter itself 

Yes,  I do have a wiring diagram (I could try to post it if it can help). But the black wire feeding the tachometer is directly connected to the LH coil. This LH coil do have a red (battery voltage) wire and a black one. This black wire is splitted to feed both LH coil and tachometer.

Manual says this black wire should read 2-4 volts but it does read battery voltage...

Here's the wiring diagram. First one is from OEM manual while second one is from Clymer.

Wiring Diagram - KZ1000J3-R2 by zxclaude1 , sur Flickr

Wiring diagram KZ1000J3-R2 (Clymer) by zxclaude1 , sur Flickr

Ok Claude, how are you measuring the voltage when the motor is running (at which points) if there was battery voltage on both sides of the coils (black wire and green wire) the the coil can't collapse the magnetic field so there would be no spark ????

Yes, I’m measuring battery voltage at both black (LH) and green (RH) coils. And engine is running great.
Someone suggested the 2-4 volts written in the manual is a typo and could be 12-14 volts instead. Could make sense.

Anyway, looks like it is a bad contact somewhere in the cluster. Today, while engine was running, I tapped on the cluster with a small rubber mallet and the tacho came back to life!!
I now have to try to find where’s the bad contact. I think I’ll open the cluster trying to soak it with brake cleaner. Thanks for your comments!! I really appreciate!

wrote:

Yes, I’m measuring battery voltage at both black (LH) and green (RH) coils. And engine is running great.
Someone suggested the 2-4 volts written in the manual is a typo and could be 12-14 volts instead. Could make sense.

Anyway, looks like it is a bad contact somewhere in the cluster. Today, while engine was running, I tapped on the cluster with a small rubber mallet and the tacho came back to life!!
I now have to try to find where’s the bad contact. I think I’ll open the cluster trying to soak it with brake cleaner. Thanks for your comments!! I really appreciate!

There is always the possibility that it is a mechanical problem, you could try carefully lubricating the needle mechanism when you are in the cluster 

The speedo was dead on my J2 when I bought it. After some basic troubleshooting I opened it up (quite the pita), it turned out that the little coil that moves the needle had broken loose on one side. I was able to solder it back and it has been working fine since, in the process I changed the electrolytic capacitors as well. So be sure to check the coil if you open it up, I guess the electro mechanical parts are similar.