1983 Yamaha Venture 1200 XVZ won't Idle after warmed up

After my 83 Yamaha Venture 1200 warms up into the operating range it won't run at an idle or under 2000 rpms. I can rev it up to all the way to the red line and it runs great, but at a low idle (below 2000 rpms) the tach drops to zero and it kind of chugs along wanting to die. I tried changing out the plugs and wires but that made no difference. I also located and changed the fuel filter. Open to suggestions.

the tach drops to zero

CLASSIC symptom of interrupted ignition signal from number two cylinder; usually indicative of a failing TCI and/or poor TCI connections.

The hotter the TCI gets, the more prone to intermittent failure.

Clean the TCI connectors.

Relocate the TCI to the cooler and dryer location on top of the airbox...and cross your fingers.

However, if the engine just barely ticks over at idle (is that what you mean by "zero"?) without applying "choke" (enrichener), but after giving it choke, it will idle OK, then that is more likely a plugged pilot circuit in one or more carbs. Plugged or partially clogged pilot circuits is also very common.