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Alternator removal struggle solution and - Is the rotor magnetically charged or not?

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  • Alternator removal struggle solution and - Is the rotor magnetically charged or not?

    Hi

    So I am doing an engine rebuild and I had some SERIOUS struggles getting the alternator rotor off and ended up testing some methods I am not proud of . To be honest I really wanted to get the crankshaft off and the alternator rotor was the biggest problem, tried heat, rotor bolts (the correct one), 2 legged puller, etc. Long story short, I ended up splitting the crankcase, etc. as had planned to do anyway and figured I could sort this out when it became a real issue and perhaps had better access further down the line. Turned out the last was true. When all else was stripped off I was able to turn the top half of the crankcase 90 degrees and simply fill the taper/rotor cavity with rust penetrant as much as possible, letting gravity pull the penetrant into the taper/rotor joint and let it stand overnight. Filled it so that the meniscus (wow, that's a blast from a high school science class past) was right at the top. This morning the meniscus (liquid level) had dropped indicating that something had disappeared into the cavity that was otherwise tighter than a catholic virginal nuns. I put in the rotor bolt as far as it could go leaving a small (2mm) gap as the washers had been removed and then hooked up my 2 legged puller and gave it a wind. It needed a fair amount of force, as in in reaching the limit of what I physically could wrench the ratchet kind of force. And then it popped the full 2 mm and met the bolt head. At first I thought something had snapped and was filled with dread a brief moment followed by a realization that it had finally come off, and nothing was broken.

    The only fly in the proverbial rust penetrant was the realisation that in the process I had used a steel hammer amongst other things to get it off and only afterwards thought about the whole "it's bad idea to use a steel hammer with steel on a magnet" thing. Now I think I know enough about principles of alternators to know that the rotor is often magnetically charged. However I did notice that throughout the struggle I didn't notice any magnetism as such, begging the questions:

    A) is the rotor supposed to be magnetic?
    B) did I destroy this magnetism by hammering on it?
    C) should I get a new rotor anyway, just because?

    So assuming you haven't checked out by now, do I need a new rotor given that I bludgeoned the one I have with a steel hammer destroying any and all a magnetism there was, or was there, this is the question?


  • #2
    I'm 99% certain it is not magnetized. I've only taken off two and they both came off easy compared to what you experienced.
    79 F full cruiser, stainless brake lines, spade fuses, Accel coils, modded air box w/larger velocity stacks, 750 FD.
    79 SF parts bike.

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    • #3
      Originally posted by Json View Post
      Hi

      So I am doing an engine rebuild and I had some SERIOUS struggles getting the alternator rotor off and ended up testing some methods I am not proud of . To be honest I really wanted to get the crankshaft off and the alternator rotor was the biggest problem, tried heat, rotor bolts (the correct one), 2 legged puller, etc. Long story short, I ended up splitting the crankcase, etc. as had planned to do anyway and figured I could sort this out when it became a real issue and perhaps had better access further down the line. Turned out the last was true. When all else was stripped off I was able to turn the top half of the crankcase 90 degrees and simply fill the taper/rotor cavity with rust penetrant as much as possible, letting gravity pull the penetrant into the taper/rotor joint and let it stand overnight. Filled it so that the meniscus (wow, that's a blast from a high school science class past) was right at the top. This morning the meniscus (liquid level) had dropped indicating that something had disappeared into the cavity that was otherwise tighter than a catholic virginal nuns. I put in the rotor bolt as far as it could go leaving a small (2mm) gap as the washers had been removed and then hooked up my 2 legged puller and gave it a wind. It needed a fair amount of force, as in in reaching the limit of what I physically could wrench the ratchet kind of force. And then it popped the full 2 mm and met the bolt head. At first I thought something had snapped and was filled with dread a brief moment followed by a realization that it had finally come off, and nothing was broken.

      The only fly in the proverbial rust penetrant was the realisation that in the process I had used a steel hammer amongst other things to get it off and only afterwards thought about the whole "it's bad idea to use a steel hammer with steel on a magnet" thing. Now I think I know enough about principles of alternators to know that the rotor is often magnetically charged. However I did notice that throughout the struggle I didn't notice any magnetism as such, begging the questions:

      A) is the rotor supposed to be magnetic?
      B) did I destroy this magnetism by hammering on it?
      C) should I get a new rotor anyway, just because?

      So assuming you haven't checked out by now, do I need a new rotor given that I bludgeoned the one I have with a steel hammer destroying any and all a magnetism there was, or was there, this is the question?
      As you are probably now well aware of the rotor sits on the end ot the crank on a tapered end / hole in the rotor and the only thing that held it on was that bolt and washers and a lot of time. For future reference they actually make a removal tool, no i don't have one either, that consists of a cylinder withe a 16mm by 1.5 pitch bolt going through it which also threads into the threads. Inserting a long screwdriver through the sides of the rotor and something to hold the screwdriver from turning and then and impact wrench on the bolt will remove it. If you don't have the removal tool just the bolt will do the job. There is a guy in Australia that sometimes frequents this forum that posted a video on youtube showing how to remove the rotor with just the bolt and screwdriver and a hammer. His handle is steptoexs11 on youtube. As to your questions concerning the rotor and whether it is magnetized. It is electromagnetically magnetized so unless you caused damage with the hammer it will probably be ok. It is a fairly stout assembly. I wouldn't recommend beating on it with a steel hammer directly so if that is what you did then who knows whether you damaged it or not. We used to have a shop in the Air Force that inspected assemblies such as these for cracks by a method called NDI (non destructive inspection) with the use of dies and black lights and other means. I used to watch them at work because they were right next door to our shop. Pieces that from the naked eye showed absolutely no damage but as they went through there testing many proved otherwise and had hairline cracks in them that would have been catastrophic in a jet.

      To make a long story short (I guess it's too late to make that statement) you should make a decision based on how much you beat on it and from my quick search on Ebay many are available at reasonable prices. Of course you never know what those were subjected too as they were removed either.
      2 - 80 LGs bought one new
      81 LH
      02 FXSTB Nighttrain
      22 FLTRK Road Glide Limited
      Jim

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      • #4
        Originally posted by cajun31 View Post

        For future reference they actually make a removal tool, no i don't have one either, that consists of a cylinder withe a 16mm by 1.5 pitch bolt going through it which also threads into the threads.
        Thanks, I actually had a tool like the one attached that had the 16mm 1,5 pitch bolt on the one leg, I bent the thinnest leg trying leverage more force to get the rotor off without any joy. I tried all the other suggested ways of removing after scouring the forums here and elsewhere.

        The rotor is still in good condition, I just wasn't sure if it was magnetised.

        Thanks for the advice.

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        • #5
          For future reference, the correct metric bolt with an impact gun will do the trick. Remember, don't start the engine for any reason with the alternator cover off, the oil galley plug will shoot right out soon as there is oil pressure.

          Click image for larger version  Name:	IMG_20220509_224426.jpg Views:	0 Size:	141.5 KB ID:	868662
          2H7 (78)
          2H7 (79)
          3H3

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          • #6
            The charging rotor is not magnetic. The rotor coil is stationary and it magnetizes the rotor through the battery. The bike won’t run without a good battery. Usually, a rotor like that is full of wire and fed through carbon brushes as is the XJ1100 or the alternator in your car. Brushes were eliminated in the XS1100 and the “rotor” is stationary. It is what magnetizes the spinning iron portion.
            Marty (in Mississippi)
            XS1100SG
            XS650SK

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