Originally Posted by RichHead
Sweet, thank you. Yeah it didn't seem quite right.
So, if I want to set the idle to 1000 for example, the tach will read 2000?
No...read the 2nd post again: what he wrote was that in the case of both /5 and /6 mechanical tachs, the cable runs at half speed to what the tach-face displays. Unless things are grossly whack-o, the rev counter's announcements will match the crank speed.
It's the sort of thing that a lot of tach-drive designers did in an effort to make it more reliable, by having the most fragile part of the system run at half speed.
There's no rule unwritten rule that dictates a 1:1 tach-drive ratio.