A simple first check, make sure your charging system works properly. When my stator went out, and my battery was dying on me, I started losing the tach and speedo before the bike died. I'm assuming this is not your issue as it has been going on for a while, but weak/irregular voltage can make a motorcycle do weird things. My previous first gen had a display issue and didn't show speed but the RPM still worked. I would also potentially look at fuses. Not sure if the dash has them but its an option.since a few months ago i noticed the tach. meter have intermittent work. and now it stopped working. i already checked connection and wires. i didnt see anything wrong. if someone can give me some advice will be much appreciated. bike its a 1999 R6.
i know electronics, so no problem to do it by my own. what you mean about comm. related?Do the first gen bikes' dash perform a power on self test that lets you check all the lights and gauges when you first turn the key in the ignition? If so, gauges typically perform a full sweep of the face. If it performs the sweep but doesn't otherwise work, the issue could be comm related. If it doesn't perform the sweep, then the problem is likely isolated to the gauge. But as Slow1stGen stated, check for proper power first and foremost.
May try opening the gauge up and touching up all the solder joints on the PCB.
If it has electrolytic capacitors, they may have aged out and require replacement.