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1978 R80 Brushes Question

nickrides

Nick Kennedy
Hi Gents
My Gen light flashed on today for just a second. I took a look at my brushes and they are about 1/8th -3/16th into the holder.
The bike has 44,500 miles. Are they shot?
When the brushes are new, are they in the holder, flush or extended out?
How difficult are they to change out? Is the soldering precise?
Thanks in Advance
Nick Kennedy
 
I bought new brushes, but just pushed down on the old ones with a pencil. They weren't making full contact. That was after some 125,000 miles, so I doubt that yours are worn away. They've charged fine since I did that about 6 years ago.
 
IF the gen light came on because of the brushes, you may just need to clean up the contact area; since 1978, you may have some corrosion or just carbon buildup down there.
 
If they are like brushes on an electric motor, with some sort of a spring pushing them down, it could be just a build up of crud on the SIDES of the brushes.

I just take a piece of wet-or-dry paper, and sand then lightly on the sides and edges and then make sure they float up and down easily for the spring to push then against the rotor.

If it doesn't then and they are too short, replace them.

Also, be sure to clean the contact surface by lightly sanding as well. One thing that also helps is the use of contact cleaner - available at most auto type stores or Grainger, McMaster-Carr or any electrical shop/store like Graybar.

The contact cleaner is designed to be used while an electric motor is running - no threat of fire. Cleans somewhat the commutator as well.
 
Thanks for the advice you guys, I will clean up the area, after 35 years young there is bound to be some funk in there!

But I am still curious...How low can they go? Is there a color difference at the max wear point?
Cheers
Nick Kennedy
 
I seem to remember that 13mm in length is the point at which they should be replaced. My /7 with 100K still has the original brushes. One issue when replacing them is to ensure that the snail spring has the proper number of winds so as to put the right amount of pressure on the brush. Other issues with replacing them are getting the nut/bolt out on the inside of the stator. Another is if you solder in new brushes, it's important to not let the solder wick up the wires, making them stiff and thus leading to premature failure. IIRC, Motorrad Elektrik sells solderless brushes.
 
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