Glad to hear that the tach is fixed.

For others that have a tach problem, one thing to keep in mind is that the signal that the tach is reading is a high voltage spike.

When the ignition module interrupts the current flow through the coil, the coils magnetic field collapses. This induces a voltage in the secondary windings, providing a spark.

It also induces a voltage in the primary windings. With the motor running, if you put a scope on the negative terminal of your coil you will see a peak AC voltage of at least 300 volts (350 - 600 typical). It will also have a high frequency component ( AC wave) that decays to zero.

This is the signal that the tach needs to register a firing event.

Kevin