i have a chance to buy a black 88 vert N/A needs a few minor things for $1000. it needs a top and the tach doesnt work 85% of the time. What would cause the tach not to work all the time?

 

Trailing coil connection, most likely.

 

If not a Trailing coil/ignitor problem, try this: Next time it does not work and then engine is running, rap on the plastic cover on the instrument cluster. If it starts working then, then the problem is a loose round connector on the back of the instrument cluster OR one of the screws on the back of the instrument cluster is corroded/loose.

Or a failed trail sparkplug that never fires can do the same thing....cause no tach signal.

 

well i bought it for $1000!!!! i drove it about 20 miles to get gas filled up and tach has worked ever since. it is in awesome shape too

 

Perhaps to start it someone pulled the EGI fues out than put it back in. This has been known to temporary disable the tach until next start.