Jumpy tach

[mastan]

Hey all:
I recall seeing a post a while ago about a jumpy tach being a symptom of some kind of electrical problem. My 78e just started giving a jump whenever I shift gears. I did a search but came up empty. At idle, or at constant RPM, it gives a steady read. Any ideas?
TIA,
Mark Stanton

[prometheus578]

The tach is operated offa one of the leads from the charging coil.
Had a tach that would sometimes play dead, hold steady or just jump around.
I swapped in a spare voltage regulator/rectifier and cleaned all the fuse conections. Which one of these actions cured the problem, I don't know.

[pggg]

Mas, the ancient plastic plug/pin connections between generator and tach can get dodgy. I've gradually ditched a lot of those plugs on my bike and replaced with single screw connecters. Not as conveniant to connect/disconnect as plugs, but at least you know your wiring connections are solid.