ok well the nuetral light isn't lighting up but the tachometer doesn't work at all. Not the light the whole gauge, the needle doesn't move at all.
Are all the fuses ok?
What year bike is this?
If it's one where the tacho is cable driven by the front wheel (I have experience with this on other bikes..), try getting the front wheel off the floor and disconnecting this cable at the tacho. Rotate the front wheel in driving direction and see if the unplugged end of the cable turns.. If it does then you at least know the cable and wheel unit are ok.
If it doesn't rotate, disconnect the cable from the front wheel and turn the inner part of the cable by hand and see if the other end rotates again.
If not, you need a new speedo cable. If so, maybe a new front wheel speedo drive unit thingy?
Also make sure the ends fit properly back in as well and that they aren't rounded and slipping.. If they are fine, then at least you know it's the tacho end that has the problem, not the rest of it.
I'm assuming this is of course how the front wheel driven speedo system works on the earlier bandits, much like on many other bikes so hopefully this is of some help but I can't guarantee anything!