Have a really weird issue although not quite sure if it is a problem at all actually!
If you could have a look at the video link below you will see my tach without any power (ie no ignition) shows 200rpm and the minute I turn the ignition is goes down to zero!
After use (ie. on power down/off) the tach is at the zero mark!
Does this imply some problem with the wiring possibly an earthing problem or is it nothing to worry about!?!