93 FZR 600 Tachometer Problems

[BikerDude]

I have a 1993 FZR 600 that I bought last fall. It was not running. Two guys had stripped it down to the frame and were going to rebuild it.
I replaced the rings on the pistons, honed the cylinders, lapped the valve seats and put it all back together.
The bike seems to run pretty well. It will idle, around 800 rpm (guess) and it wraps up to 6k rpm (guess) without a problem.
However I can not get the tachometer to work. There appears to be no signal, despite getting about 8 volts on the gray signal wire.
I bought a replacement tachometer and hooked it up. It still does not work
I am powering the new tach directly from the battery using long leads, so it is not a power issue.
I replaced the digital ignition system. Not cheap, and that did not help at all.
I tried jumpering off the gray wire right on the coil to the signal on the tachometer. Still nothing.
I ohmed the gray wire to ground, with the bike off its not grounded out.
I need some more ideas on how to troubleshoot this problem.
The last thing, I think would be to just replace the coils, but the bike will run so I am doubtful that will help.
What would you check with the bike off?
What would you check with the bike idling?
Would you like a picture of something to help?

Thanks