Tachometer not consistent - Help from the electrical wizards

You can buy the new circuit board that fits right into the can and upgrade it to solid state. Also, I was told by the powers that be that if you want to lube the tach mechanism, only use Slick 50 “1” lube, no other lube is acceptable. The new circuit board also has a calibration feature, and direction how to do it. It was $79 when I bought it, not sure what it runs now!