erratic tach

[jayel]

1980 SG cruising at 60 mph tach sits steady at 4000 rpm a few more rpms and the tach jumps 4500, 4000, 4500, 4000, once I get above that range it sits steady again 4500 is steady, any ideas or anyone seen this before? first question search hasn't anwsered for me

[motoman]

Might wanna pull off that left side ignition cover and while idling, take both hands and pull on pick-up coil wires every inch to try and seperate. If the outer shieving stretches like a rubber band, you've found a break in wire. Plug-in behind fuse panel is also a good source for electrical issues, as are others if they've never been cleaned and sealed with dielectic grease. Doubtful a tach issue.........it's just lettin' you know there ARE connection issues somewhere.

[BA80]

The pickups haven't got a thing to do with the tach motoman, it runs off the pulses from the alternator.

jayel, check all the connectors from the alternator particularly the plugs behind the fuse panel. (white wires) Clean them and put some kind of electrical grease on them.

Unfortunately the only other thing you can do is tear into the sealed body of the tach to try and repair. That sucks I can testify. There is an integrated circuit in there that goes bad usually so you might just try to find a different tach if all the connections are good,

[jayel]

checked pickup wires earlier (seen it mentioned a few times :lol haven't done the Di-E grease yet can't find my tube I know I have, went thru a Yam XS650 a while back haven't found the right pile of stuff yet or the darn cats have hidden it, did pull that alt plug tho' definately dirty we'll see how it does

[Rasputin]

I had a very similar problem a few years back. I am quite sure it is a dirty or loose connection that you are looking for. I cleaned up everything I could find back then and it worked but I could not tell you which connection it was as I did a wholesale type clean. It could be as simple as a loose wire in the headlight bucket connector, so you may spend some time tracking it down.