Alternator brush question

[pumps]

Just got out my new trusty Harbor Freight digital caliper http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47256
and pulled my brushes out to measure them . Inner was 10.72 mm and the outer was 14.41 mm. How long do these last? Bike has about 16000 on it. The manual says new ones are 14.5 mm so I wonder if these are original.The manual also says to replace at 7 mm so I guess I'll let them ride. Do they normally wear so differently?
I notice the philips screws that hold them in are kind of boogered up. I might get some metric allen screws to put in if I can find them.
I'll clean the rings before I get it all together. Any other things I should be aware of?

 

[yamaman]

Hey Pumps, I read one of pamcopetes posts a fair while ago about brushes. He made some sense of it!

The outside brush will do a lot more miles than the inside i.e. one rev on the outside is like 4 on the inside. He suggested swapping them from time to time. Funny that yours have worn the other way.....Maybe I got it wrong, but it seems like a good theory to me.

He also says to clean the rings with an eraser.

 

[pumps]

I did read Pete's info about using an eraser. What about electrical contact cleaner..think I have some DE-Oxit. I wonder if these had been swapped around by a PO?
At any rate I have been charging ok previously. I wanted to check them while I had the left cover off. Probably put them back in and call it good. Except for the boogered screws.

 

[Sundie]

the only cleaner i would use is possibly brake cleaner. If it's working, don't f' with it.

 

[weekendrider]

Pumps I'd say they have been replaced or you have been lucky in finding that one exceptional set. Mine don't seem to last that long. If you replace the screws watch the length. It's easy to get into the rotor.

 

[retiredgentleman]

Pumps;
The brush that's at 10.7 mm is well worn. It should be replaced when it gets down to 9.5 mm (3/8"). You should be OK to run those brushes this year, and replace them next year.

I find my brushes don't wear rapidly at all, and they are both wearing evenly. I just checked my brushes. New length was 0.571". Now after 4050 kms, they both measure the same at 0.562".

Perhaps there is a difference in the hardness of the carbon when manufactured. This would explain why we see varying wear rates. However, you would expect the outer brush to wear faster??

 

[Gordon]

I am with RG on all counts. You should get the season out of them. What I did was used 400 grit wet/dry sandpaper where the brushes ride. My brushes are also worn to 2 different lengths.I think it had to do with the way I re-installed them last season. The little bastards just didn't want to cooperate. This year I used a small set of hemostats to hold the spring down so I could 'flip' the holder in place. Worked pretty good, just had to work fast once they were in place before the final tightening of the hold down screws. You'll see what I mean when you re-install them.

 

[thomariz]

I have a '83 xs650 that won't rev over 3000rpm it's strong aside from that, voltage seems good on the battery however iv been reading that if the Cdi unit isn't getting enough power then it won't initiate the advance and won't let it rev through 2500-3000rpm. If the brushes were worn could this possibly be causing this problem? Thanks!

 

[Gordon]

Has the bike alway's run like that? Doe's it still have the stock exhaust system. or head pipe's? The stock system's had a problem with the inner pipe collapsing and not letting the exhaust flow out of the engine. To find out if it has collapsed, take it off, take the muffler's off, and roll a small ball through the head pipe.The ball should be close to the inside diameter of the pipe so as to not get a false reading if the ball is too small. A marble is too small, unless you got an Aggie.
I don't think it's a charging problem from your description.

 

[Megatron]

Im having a charging issue, the bike is chewing through batteries, so I took the left side apart to examine the rotor and alternator, the rotor's giving me about 5 ohms so I think its fine, and the alternator appears to be ok. All my wiring on the bike looks to be squared away, so I noticed the brushes did look pretty worn down, like they might not even be making contact with the rotor, I didn't pull them off, but could my charging problem simply be some really worn out brushes?

Im going to pull them off and measure them, whats the ideal measurement for these (1975 xs 650)

Here are some photos just for a visual

 

[5twins]

Yes, worn out brushes can stop the charging. When they get too short, their spring doesn't push them in hard enough against the rotor to make good contact. As mentioned above in the 1st post, new length is 14.5mm, wear limit is 7mm. Your inner slip ring looks pretty dirty, time for a cleaning I'd say. I use a little chrome cleaner on a rag. Shines the rings up quick and easy. I follow with a wipe down using electrical contact cleaner to remove any polish residue.

 

[mrtwowheel]

Clean the carbon off of the stator, I've had shorts to ground from the excessive carbon. I use Walmart's Tech Lubricant and air pressure to clean the stator, It's a fragile thing, just spray and blow off, no scrubbing. That inner ring on the rotor looks like it was causing some heat, I use a green Scotch-Brite pad and Brasso on the rotor rings, wiped with rubbing alcohol afterwards. You may have gotten to these issues just in time. Carboned up rings have caused erratic charging for me before.

Scott

 

[TwoManyXS1Bs]

You may want to consider that it's the outer slipring that has a problem. According to some slipring inspection and carbon trail patina/tarnishing discussions in this thread, it would appear that the inner slipring and brush have been making proper contact.

http://www.xs650.com/threads/dead-rotor-best-options-to-fix-replace.36211/

Notice the coppery cleanliness of your outer slipring, with a couple of short/odd dark tracks. It would appear that the outer brush may have been jumping or skipping over most of the slipring surface. Might look closely for possible slipring damage from a previously installed too-long brushblock screw, like this:

 

[mrtwowheel]

On a working rotor with good brushes I've always found almost spotless copper with a few streaks of carbon, just like the cleaner one there. On rotors that the charging voltage jumps around to different voltages, but still below cook your battery voltage, I have found rings just like the black one there. I can't describe exactly why or how, but I was taught that the carbon from the brushes gets mostly blown away from the rings on a well working rotor, and these concepts have worked well for me and others for quite some time now.

 

[Megatron]

Thank you for the thoughtful and helpful replies! I am going to take this information and see what I come up with, I will definitely clean the rings and I measure the brushes

@mrtwowheel about cleaning the stator, you mean get the black/hard gunky stuff off those copper blocks and wires? But dont brush it as its too delicate right?

 

[mrtwowheel]

Thank you for the thoughtful and helpful replies! I am going to take this information and see what I come up with, I will definitely clean the rings and I measure the brushes

@mrtwowheel about cleaning the stator, you mean get the black/hard gunky stuff off those copper blocks and wires? But dont brush it as its too delicate right?

Yes, that stator is very fragile and delicate. Mostly what you need to clean is the space between where the wires enter and the aluminum frame close to those wires. Yamaha never envisioned the carbon build up from years of use on these parts. Clean the rings, even if it takes wet-or-dry sandpaper, then polish to a smooth non-abrasive surface, new or good brushes, then do the charging tests. I bet you'll be back in business.

Scott

 

[Megatron]

Okay thanks for the advice.

I gotta buy a new battery and brushes and Im hoping that will solve it.

Just pulled the brushes off

 

[mrtwowheel]

Yeah, those are short brushes.

 

[TwoManyXS1Bs]

On a working rotor with good brushes I've always found almost spotless copper with a few streaks of carbon, just like the cleaner one there. On rotors that the charging voltage jumps around to different voltages, but still below cook your battery voltage, I have found rings just like the black one there. I can't describe exactly why or how, but I was taught that the carbon from the brushes gets mostly blown away from the rings on a well working rotor, and these concepts have worked well for me and others for quite some time now.

Avitar shopping, are we Scott?

It wasn't until that "rotor runout" thread that I learned of the slipring patina.
A web search on "copper slip ring carbon patina" finds more info, like:

The way things work around here, I'll throw out my ,
and see if it sticks to the fanblades.

 

[Megatron]

Figured I would follow up with a report on my progress so far.

Upon arrival of my new brushes and battery I got to work. I first sanded down my rotor with a 600 grit wet sand paper, just to clean it up, I then wiped all that down and made sure it was clean. I was shocked by how much dirt was on the rotor. Now it looks like new. After that I replaced the brushes with some fresh new ones, replaced the battery and then sealed everything back up.

(Getting those new brushes on the stator was a total pain in the ass)

Bike fired right up and sounds and rides great so far, but only time will tell if this was truly the source of my battery problems. If my battery maintains its power over the next few days I will know I fixed my problem.

I will update when I know for certain.

Thanks for the help amigos