There are only three connections that need to be right (assuming the internals
of the tach didn't take exception to you disconnecting the tach from its
rightful place):
First: Ground. The bane of all Smiths instruments. On the Tiger the instruments
are grounded by a daisy-chain black wire that connects to the dash crossbar with
a star washer.
Second: 12V fused ignition-switched power. A green wire that connects to a spade
lug terminal on the back of the tach.
Third: The ignition coil-current sense wire, which is white. 12V ignition
switched, unfused, it makes a one-turn loop around a little metal U bracket that
bolts onto the back side of the tach. The metal U bracket forms part of a
transformer core with the corresponding current sensor on the inside of the
tach. The ends of the U must be inserted into the tach body, and should make
contact with the two metal tangs on the receiving end. Sometimes the U-bracket
has a molded plastic insert to help guide the wire - that just depends on how
many mechanics the tach has seen.
If you reinstalled it after rewiring the coil, check those connections. Unless
you're using something very similar to the factory wiring scheme, the white wire
won't carry the current pulses required to make the tach sensing circuit work.
Good luck.
Theo
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