Tach needle jumping around...

[JonnyO]

A quick google search showed me nothing. 1981 XS 1100 Special
Couple days ago I thought I was seeing things 'cause I thought I saw the tach needle jump. Today there's no question-it's going to zero and then dancing around and back to zero... but not holding the speed.
Figured I'd ask the pros what the repair entails. I'm hoping the cable just needs to be lubed but have no clue, really. I can follow your guys tips though.
TIA- Jonny in AZ

[bikerphil]

There is no cable driving the tach, it gets it's signal from the alternator. I suspect that maybe the connector plug behind the fuse panel may be the culprit. Before you go digging for it, with the bike running, check your alternator voltage output with a meter at the battery terminals. When you rev the throttle, you should see a decent increase in voltage, 13V+. If it isn't increasing, then I would check that connector for it being melted.

[cajun31]

A quick google search showed me nothing. 1981 XS 1100 Special
Couple days ago I thought I was seeing things 'cause I thought I saw the tach needle jump. Today there's no question-it's going to zero and then dancing around and back to zero... but not holding the speed.
Figured I'd ask the pros what the repair entails. I'm hoping the cable just needs to be lubed but have no clue, really. I can follow your guys tips though.
TIA- Jonny in AZ

Just want to make sure you saw this repair tip from the maintenance section. Tachometer Wobble - XS11.club Forums
If you decide to try to lube that small ball bearing don't go overboard.

[JonnyO]

Just want to make sure you saw this repair tip from the maintenance section. Tachometer Wobble - XS11.club Forums
If you decide to try to lube that small ball bearing don't go overboard.

Thank you for the suggestions! I will post if and when I'm able to resolve.

[JonnyO]

So how do you get it further apart than this? I'm afraid to pry or pull any harder to separate the housing to access the board.
Thanks!

[bikerphil]

Jonny, you basically have to cut metal to get into the tach, so before doing so I would make sure the electrical connections running to it are in 100% good shape. If your tach reads zero and then comes on and off, it is most likely an electrical signal problem outside of the tach.

[JonnyO]

Jonny, you basically have to cut metal to get into the tach, so before doing so I would make sure the electrical connections running to it are in 100% good shape. If your tach reads zero and then comes on and off, it is most likely an electrical signal problem outside of the tach.

Huh? Any thoughts on what and where I should check for those signal problems Phil? I thought once I removed the housing I'd be able to recognize where I should drop a little oil. I don't.
THe " connectors "( black brown and white all seemed to be pretty snug when I unplugged them after taking the bulbs out, ).
I may have worked at an auto repair shop for over 15 years but I'm still clueless until I've actually done a repair a time or two. Not very mechanically inclined. I've been amazed watching those who are.
Should I take a little 400 grit to them or put any grease or oil on 'em?
Thanks.

[bikerphil]

Do like I suggested before, check your charging system voltage with a meter. The alternator supplies a signal to the tach. If the signal is flakey, you'll have a tach malfunction.

[cajun31]

This maintenance tech tip might help with what Phil is telling you to do. Charging System/Tachometer - XS11.club Forums

[JonnyO]

This maintenance tech tip might help with what Phil is telling you to do. Charging System/Tachometer - XS11.club Forums

TY! That should answer my next question without having to ask.

[JonnyO]

There is no cable driving the tach, it gets it's signal from the alternator. I suspect that maybe the connector plug behind the fuse panel may be the culprit. Before you go digging for it, with the bike running, check your alternator voltage output with a meter at the battery terminals. When you rev the throttle, you should see a decent increase in voltage, 13V+. If it isn't increasing, then I would check that connector for it being melted.

To illustrate the depth of my mechanica skilz and expertise, when I reinstalled the lights back in the tach I had the high-beam and neutral switched... which I found out only after putting it and half fairing back on the bike and going for a quick ride to see if that had magically repaired the problem. Of course it hadn't. lmao Perhaps I should have checked before fully assembling it.
I'm going to see if I can find a coloring book with pictures.
Gonna look up how to use my voltmeter to test the alternator output from the battery. Huh. I wonder if the car battery tester I have ( somewhere ) would test the bike's alternator as it will on cars..?
Have an appointment at the VA, in an hour, and a bunch of errands to do but will test it as you suggested when I'm done.
Thanks again.
Merry Christmas to all.
HE LIVES!!!

[JonnyO]

To illustrate the depth of my mechanica skilz and expertise, when I reinstalled the lights back in the tach I had the high-beam and neutral switched... which I found out only after putting it and half fairing back on the bike and going for a quick ride to see if that had magically repaired the problem. Of course it hadn't. lmao Perhaps I should have checked before fully assembling it.
I'm going to see if I can find a coloring book with pictures.
Gonna look up how to use my voltmeter to test the alternator output from the battery. Huh. I wonder if the car battery tester I have ( somewhere ) would test the bike's alternator as it will on cars..?
Have an appointment at the VA, in an hour, and a bunch of errands to do but will test it as you suggested when I'm done.
Thanks again.
Merry Christmas to all.
HE LIVES!!!

Well, if I used the meter properly, it went from around 11 to 14.6 when I revved it.

[LAB3]

Sounds about right!

[JonnyO]

Sounds about right!

Maybe the tach is just no good. Still puzzled. Mechanic buddy said to put voltmeter switch at 20. I did-Idle at around 12.36 revs up to 15ish.

[LAB3]

15 sounds a bit too high, are you running a lithium battery? I'd be leery of anything higher than about 14.4 with a lead-acid battery.

The tach itself is reading off one of the stator windings which would be an AC voltage somewhere in the 50v+ range.