Unusual Electrical development

[79XS11F]

Last year my 79 restored bike developed a tack needle bounce. I changed out the alternator and the tack but the problem remains. On my first run this year I noticed that now the fuel gage is trying to move to the empty position against the actual fuel level in the tank. So the fuel level needle is vibrating downward.
Both of those devices are in the same gage. I also see that my 2 year old battery becomes discharged too quick for my liking. I have not confirmed the voltage regulator as being good yet and wonder if it could be the issue? Or is it something else. I can't see it being in the harness because the harness is new front to back and everything worked A-OK until last year when the tack started acting up.
Rob

[crazy steve]

Yeah, I'd look at the regulator and the alternator connections while you're at it. The tach bounce would likely be in the connector behind the fuse panel (unless the tach is failing, but you say you've replaced that). If the regulator is failing, it may be allowing some AC component through into the system and upsetting the electronics, and would also account for your poor charging.

The other thing I'd look at is the gauge mounting. If the rubber dampers are worn, you may be getting excess vibration in the gauge and that's very hard on the gauge movements. There shouldn't be any free movement of the gauge in the mounting shell.

[ManagerMike]

Sounds like a good candidate for a grounding issue. I'd double check battery to engine to frame grounds.

[79XS11F]

Mounting rubber is in good shape as are the dampers. Engine has some vibration so it's time to check the valve clearences since the rebuild. Ground "may" be an issue but everything else is working fine. I am planning on tuning up, checking valve clearences and running electrical tests on the weekend. I will post what I find if I discover what the cause appears to be.
Rob

[79XS11F]

This electrical issue proved to be just the same tach bounce that I had last year. I pulled the gage and discovered that the fuel gage needle is "free" floating so it was just vibrating in the gage. My battery however seems weak. it will have difficulty starting the engine but show a full charge within a half hour of being put on the charger. So I guess the next tests will be battery condition , voltage regulator and stater output.
Rob

[skids]

Batteries can develop a "skin charge" showing good voltage but no capacity. You need a load test to determine the condition of it. The fuel gage (standard?) should not vibrate or wiggle rapidly with the current that it sees from the sender. It is controlled with a bimetallic tine to deflect the needle and it is wrapped with a "toaster" coil. I don't think it is capable of reacting that quickly to changes and is naturally dampened. The tach wiggle...I wouldnt lose too much sleep over that as it is not necessarily indicative of a bad charging system...unless you know for certain that you do have a bad charging system!

[ManagerMike]

See if this helps...

http://www.xs11.com/xs11-info/tech-t...er-wobble.html

or this.....

.http://www.xs11.com/forum/showthread...highlight=tach

[79XS11F]

Batteries can develop a "skin charge" showing good voltage but no capacity. You need a load test to determine the condition of it. The fuel gage (standard?) should not vibrate or wiggle rapidly with the current that it sees from the sender. It is controlled with a bimetallic tine to deflect the needle and it is wrapped with a "toaster" coil. I don't think it is capable of reacting that quickly to changes and is naturally dampened. The tach wiggle...I wouldnt lose too much sleep over that as it is not necessarily indicative of a bad charging system...unless you know for certain that you do have a bad charging system!

Thanks for input skids but when I say free floating I mean that the needle will go from empty to full when the gage is in my hand and turned sideways so it is just plain broken.
The tach needle is not so much wobbling. it is bouncing. Above 4K it will bounce to 6 or 7K and back and forth as soon as the throttle is turned.
Rob