The tach gets its info from the ignitor so yes, a failed ignitor would cause the tach to act up (pin 15 I think is the take-off). If the tach were the failure point Triumph would have issued a service bulletin; their silence means they don't really know if it's heat, electrical surge, or just spotty manufacturing. That said, you can be darned certain they know the mounting point is problematic just from the fact that standards don't have this recurrent problem.
