Dim lights at idle

When idling, the headlight is noticeably dim. Revving up to about 3k and everything brightens up nicely. I also noticed the horn doesn't work right unless the rpms are up. Finally, I have problems with the turn signals not flashing when idling at stop lights.

If this is an alternator problem, why isn't the battery strong enough to power everything? I don't have any problems starting the bike.

 

This symptom is pretty common.
It usually means that your Alternator Brushes are beyond the service limit and need to be replaced.

It gets to be a viscous circle.
Bad Brushes cant make contact with the Alternator Rotor and develop a resistance and arcing further reducing the current flow and damaging the Rotor Face.

The battery doesn't get charged effectively.
The Voltage Regulator becomes overworked and can overheat.

Pull the Alternator Cover off.
Look inside at the housing for the Brushes.
You should see a wear limit line on the Brushes.
If you don't ... and the brushes are 10mm or less ... replace ASAP!

 

the symptoms as described can also mean a loose main ground. My lights would din at an idle I cleaned and retightened the batt. posts and it was good as new. My not be your problem... just saying

 

Will I need an impact wrench to get the cover off?

 

Shouldn't, I believe it's just 3 allen head bolts.

 

You might have to whack the Ratchet to break loose the Cap Screws retaining the Alternator Cover. But, you shouldn't need a genuine Impact Tool.

They might even come right off without a fight.
Treat the threads with a bit of Anti-seize and you'll be able to open the cover for inspection real easily.

 

Where are the brushes? I am confused :?

 

The Brushes are inside the COVER!
On the Inside of the Cover there is a Mounting Bracket with two Carbon Brushes.

The Brushes should have a wear-limit mark on them.
If you don't see the wear limit marks ... replace the Brushes.

Follow the Pigtail that comes out of the cover.
That little platform with the two Carbon Brushes are the Alternator Brushes that contact the Rotor Face.

 

Oh! I see. I'm no engineer but I would describe those as contacts instead of brushes as they have no brushy looking parts. Thanks for your help Rick. I looked and it seems the brushes have been replaced as there was lots of material above the wear line. Probably 5-6 times as much as between the wear line and the bracket that holds the brushes...

I noticed some grooves on the inside track of the copper disk that spins inside so I smoothed them with a bit of sand paper. (think brake disk grooves) I noticed some old oil inside the case. Is that normal?

I checked the ground connection on the battery and everything looked clean and tight. I did disconnect the negative on the solenoid aand cleaned it as there was a little corrosion.

I went for a ride, and things seemed a bit better, but things always "seem" better after a little wrenching...

I put it on the charger for the night and we'll see tomorrow if the symptoms are improved. I'll post an update...

 

update: - all is about the same. I made sure the battery was completely charged and did a few miles around town today and there really is no improvement. I will go ahead and clean the battery terminals and tighten them up tomorrow.

 

After you clean the Battery terminals ... clean the Main Ground Strap Terminal and the surface where it connects to the engine for Ground.

If you haven't up-graded your Fuse Panel; you should really consider replacing that.

A good many electrical gremlins are eventually traced right back to the OEM Fuse Panel.
They do not age gracefully!

 

The charging system really doesn't produce charging voltage until 2K rpm. Below that the battery runs the show. With everything working properly the lights will get brighter as you rev to 2K.

The battery should have enough juice to run the horn and signals. If your connections are good perhaps you need a new battery. It should show at least 12V at the battery when idling.

 

What should the voltage be at 3K?

 

14.2 Volts -to- 14.5 V is the design parameter.

 

I measured and I am only getting 11.9 at idle and 12.9 at 3k rpm. What could be causing this? How do I get the oil cleaned out?

 

Dave check the three wires that come up from the alternator that go into a connector under the gas tank. I just found one of the three was burning the plastic plug. I sniped the plug off and installed connectors and my 750 is right up there at 14.3 volts at 3K. Good Luck

 

Now, you need a Manual that contains Electrical Troubleshooting.

That you don't see 14 Volts at 3,000 rpm's needs to be worked-ouit by checking the individual components to specs.

It could be something as simple as replacing a bad Voltage Regulator.
But the races on the face of the alternator rotor could be burned needing cleaning or replacing the alternator rotor.

 

I sent a ten dollar bill to the xjcd guy last week. Hopefully I will receive a cd soon.