Electric Trouble - 1977 XS650

[MadHatch]

Hello all!
And thanks for all the help with other posts in the past.

I'm having a bit of trouble with the electric on my bike. My battery seemed ok, I charged it, and it held charge.

But after starting it, the light will flutter and eventually it will cut if the bike comes to a stop light or stop sign. Does anyone know what this may be?..... before I start digging into a full diagnostic.

Thanks!

 

[Newagerocker]

Hello all!
And thanks for all the help with other posts in the past.

I'm having a bit of trouble with the electric on my bike. My battery seemed ok, I charged it, and it held charge.

But after starting it, the light will flutter and eventually it will cut if the bike comes to a stop light or stop sign. Does anyone know what this may be?..... before I start digging into a full diagnostic.

Thanks!

 

[Newagerocker]

Might be alternator brushes are worn to the limit.

 

[MadHatch]

I'll check the alternator brushes next.

I just read up on the main fuse, could it be this? Or would the main fuse be a different outcome.

 

[Newagerocker]

Glass pencil type vibrating in the fuse connector making poor electrical contact is a possibility.

 

[MadHatch]

Sorry for all the confusion, I am a newb to all of this. but willing and eager to learn. I took several photos of the bike. And attached them below. Can you tell by the photo if my brushes are worn too short? Should I take off the entire casing and take out the stator to find out if the brushes are too worn?

Sorry for how obnoxious i'm sure this sounds. Desperate to learn and get the back running!

 

[650Skull]

Need to remove them and measure. 1/4", 7mm minimum

Low idle can cause the symptoms. Should be around 1100/1200rpm

 

[B Burdine97]

Just remove the 2 phillips screws and you will be able to remove the housing that the brushes mount onto and you can see the brushes. When they get worn down they begin to stop making full contact with the alternator, thus not transferring the full amount of power available to the various places on the bike. Not sure what the spec on those are and how long they are suppose to be.

 

[B Burdine97]

650skull you beat me by a minute.
He could possibly be getting a weak alternator as well though correct? If the brushes are in spec and your certain your connections going into the fuse box are good, then your alternator could be getting weak.

 

[grizld1]

First off, when you write "it will cut," do you mean that the headlight fails or that the motor fails?

This may sound a little harsh, but it's well meant: you've been using an internet forum as a substitute for a service manual, and that's not a good way to learn. A better way to go about it would be to read, look, think, then ask.

 

[XSLeo]

Your bike being a 77 uses three screws that hold one brush in place a nd one screw for the other.
Looking in your pic . the black wire, upper left screw is the first screw holding the negative brush in place, the second screw is directly right from there, third is down from second. There is a mounting strap under all three of these screws.
The positive brush is held in place by the remaining screw.
Remove these screws and pull the brushes out. Watch closely at ho the wire wraps around the metal strap and fiber plate. reinstall the same way.
Once out measure the length of the carbon part. The book calls for 1/4 in. On old brushes this may not be enough, as the springs age they get weak, this won't supply enough pressure to hold the brush tightly to the slip rings, about 3/8 inch is more often a good place to change brushes.
As grizld1 said, a repair manual is the first tool you should get for any new machine, it will become your most valuable and most used tool in your tool box.
There are places online to download manuals, like biker.net, I like real books, searching Ebay is a good source of both the Clymer and Haynes books as well as Yamaha factory books.
Leo

 

[5twins]

You haven't performed the first basic test to see if you even have a charging problem. Clip a voltmeter to the battery terminals. At idle you should see around 12 to 12.5 volts. Revved up to about 3K, you should see around 14 volts. If you see no increase in voltage when you rev the bike then yes, you do have a charging problem. No sense tearing into the electrics until you confirm they are the problem.

These are metric bikes. Get yourself a 6" steel rule marked in MM down one side. It will make your life easier because most of the specs are given in MM. The brushes are 14.5mm long when new, 7mm is the wear limit.