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I have a used Harley rotor in the garage. It is off of my Shovelhead. It just was replaced during an upgrade to a Cycle Electric unit, not because of a problem. One of the magnets has fallen off. I know this was oily when it came off, but I don't remember squirting it down with brake cleaner as it was just an extra, take off part, but perhaps I did? Anyways does Brake Cleaner attack the adhesive on alternator rotors? Or did this rotor have a defect? The magnet that came off is still very strong magnetically. I am just curious more than anything. This rotor is now junk as far as I am concerned.
ETA: I did drop this on snow / ice this winter, and that is when it loosened the magnet. I dropped it about 2 feet and it hit snow covered ice. It wasn't like concrete or anything.
They often come loose if someone uses an impact gun to remove the nut. Could have been waiting to fall off and your little drop did the trick. My 82 looked like this when I removed it:
The non encapsulated magnets like that had a habit of coming loose, any good bump on the outer shell can pop one. After the second one ate up on mine I went to the older rotor with the brass cage holding the magnets in, problem solved. Issue I have with the newer rotors is the spline area tends to wallow out on them after time. They don't have that bit meaty spline boss like the old rotors.
The rotor was installed and unistalled by me with no impact wrench. Cycle Electric said it was probably from the drop. They also said I could glue it back on with good epoxy.
Those magnets , when they break loose are kinda handy for other uses , I use them in my parts washer to collect metal filings and in my Sunnen hone to collect all the metal that comes off the cylinders when you are fitting a new set of pistons . Last October I changed the oil in my hone it cost me $350 for the oil !!! at that price , I'm gonna hope my magnet trick extends the life of the oil . I've done two sets of cylinders since then , the magnets are capturing a fair amount of the metalic particles
Last edited by Gearhead88; Mar 14, 2021 at 08:46 AM.
We use them to hold light sand paper in the 2 wash tanks - and papers on my tool box - have one on the Bridgeport and lathe as well as boosters on the surface grinder - they are and have been tools in my shop since the first one we did with loose magnets mid 80s maybe
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Rotor Magnets
