I've had two tach's go bad. They work but read higher RPM than the engine is really turning. I didn't notice if anyone mentioned adjusting the screw on the throwout bearing. That was my problem and I totally overlooked it.
Its just been assumed that MC750 has been adjusting the clutch correctly. The adjuster at the clutch is a good idea.
Loosen the cable completely. Loosen the lock nut on the adjuster on the clutch, behind the chrome cover. Back the screw out. Run it in till you feel resistance. Back it out a 1/4 turn, hold it while tightenin the lock nut.
Take out as much cable slop as possiible with the adjuster on the end of the cable that enters the clutch cover. Fine tune it with the adjuster at the lever.