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TOPIC: Starter magnets loose

Starter magnets loose 11 Jul 2018 17:07 #786810

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Hey guys! My starter began operating intermittently and i removed it today for a look. The magnets on the can are loose and spinning freely, rearranging themselves. As you can imagine, results are not favorable. I don't know how they were originally held in place, nor do i know the exact placement of them in the can. Do i have options on reattaching them to the can or must I replace the starter? The commutateur is in good shape and brushes have life on them. It would be a shame to replace it, but I've not ran into anyone that has fixed this issue.

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Starter magnets loose 11 Jul 2018 17:11 #786812

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Don't they have windings?
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
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Starter magnets loose 11 Jul 2018 17:14 #786813

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SWest wrote: Don't they have windings?
Steve

Some starters use electromagnets, but his appear to be solid permanent magnets.

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Starter magnets loose 11 Jul 2018 18:31 #786823

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I would degrease the can and glue the magnets back in place and separate them with some spacers, give it a try. You can´t lose nothing.

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Starter magnets loose 11 Jul 2018 22:34 #786838

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Scirocco wrote: I would degrease the can and glue the magnets back in place and separate them with some spacers, give it a try. You can´t lose nothing.


Exactly! He can estimate / measure the positioning using the laminated core on the armature and position them so that the long bolts can still pass through to bolt it together. I assume the spacing would be the same on both sides.

A good cleaning and some JB weld, and they will never come loose again. :-)
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Starter magnets loose 13 Jul 2018 10:59 #786895

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I didn't know with the heat if the magnets would stay put with jb weld. Guess they might. 
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Starter magnets loose 13 Jul 2018 13:23 #786905

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One1 wrote: I didn't know with the heat if the magnets would stay put with jb weld. Guess they might. 


 This is my rotor magnet that broke when I had to fix my starter clutch a few years ago. The grey stuff is JB weld. I replaced the stator a few months ago and the rotor magnets looked the same as when I took this pic.

JB weld is a 2 part epoxy, so I imagine it will hold up better than any 1 part tube adhesive. There is also magnetism that helps to stick things together.

Decide for yourself.

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Starter magnets loose 15 Jul 2018 19:17 #787017

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Please tell me I'm not going nuts. I thought i had a bad one way bearing, but i swear the starter is running backwards. It's turning forward towards the magneto. Engine rotation is towards the back of the bike, "to the right", correct?  I have a crack in one of the 2 magnets and i think it's reversing polarity. 



Unfortunately everything is lined up correctly and i can't think of a way to reverse the internal polarity as it all notches into place. I guess this crack has forced me to buy another starter. 


s20.postimg.cc/jrhcynil9/20180715_180316.jpg

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Starter magnets loose 15 Jul 2018 22:57 #787023

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One1 wrote: Please tell me I'm not going nuts. I thought i had a bad one way bearing, but i swear the starter is running backwards. It's turning forward towards the magneto. Engine rotation is towards the back of the bike, "to the right", correct?  I have a crack in one of the 2 magnets and i think it's reversing polarity. 



Unfortunately everything is lined up correctly and i can't think of a way to reverse the internal polarity as it all notches into place. I guess this crack has forced me to buy another starter. 


s20.postimg.cc/jrhcynil9/20180715_180316.jpg


 Wow, that starter sure is running backwards. I would double check the brush orientation to the armature. If you reverse the polarity on a permanent magnet DC motor, you also reverse the rotation.  
 I doubt the crack is causing this, since the magnetic lines of force would still orient in the same direction. Not so sure if switching the magnets themselves would cause this. 
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Starter magnets loose 16 Jul 2018 00:39 #787024

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I googled permanent magnet DC starter motor running backwards, and ran across this post made by some guy named Ebb's Speed Shop.  I did not post this, but I did copy / paste it here.

 A little side note: A lot of DC motors are optimized to run one direction, and are built based on the RPM the motor is designed for. DC motors have "timing" believe it or not. The timing is related to the position of the permanent magnets to the armature, and of the brushes to the commutator. Ideally, you want the magnetic flux in the armature to peak right when the poles of the armature are in the midst of the strongest part of the permanent magnet's flux field. So there is a little "advance" built into this timing, since it does take a short time for the flux to build in the armature. Now if you take this same motor and reverse the polarity, it will run backwards, but it will not produce the torque nor the speed that it does when running in the "proper" direction.

This is the thread:  www.jalopyjournal.com/forum/threads/can-...ors-polarity.259628/

And yet another copy / paste from the Rad One:  (note, I did not edit all the typo's, but chrome did highlight them all for me.) :-)

Most DC motors I've messed with will turn the other way when reversing the polarity. But to get the same torque or rpm in the reverse direction you have to be able to adjust the timming. Timming is the relationship between where the brushes come in contact with the commutator segments to where the field coil reacts with the armuture windings. The starter bellhousing were the brushs sit must be able to rotate to do this and all of them are fixed with index notches and bolts.

Link to the thread:  forum.miata.net/vb/archive/index.php/t-104550.html

 It sounds to me as if the magnets are not in their exact positions, because everything else is set with notches and pins to locate them in relation to the armature and magnets. 
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Last edit: by old_kaw.

Starter magnets loose 16 Jul 2018 01:18 #787025

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Another copy / paste: 

RailmanJD318 had the answer: 

The magnet polarity probably got reversed. Is the can portion the same either way 
(180' rotation)? If so, put back together 180 deg from where it's at now. 
Joe

In_Exile got it working again.. magnets were backwards: 

After doing research, sounds like things like this can change polarity. I shaved the key off the outside of the case, flipped the case/magnet around, put her back together and vwalaa, new starter. I think in screwing with starter I changed the magnetic poles. Same as the screwdriver magnetizer/demagnetizer  tool  if you know what that is. Anyhow, learn something everyday.

www.mytractorforum.com/44-small-engines-...spins-backwards.html
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Starter magnets loose 16 Jul 2018 09:29 #787051

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Oh it is definitely a Field Effect reversal but these magnets have a glue outline where they used to be and I put them right back where they were when you break a magnet it starts to resist itself whereas it pushes against the break if you try to stick it back together and it changes the polarity of it overall adding a new field in the middle and I think I'm just getting a Field Effect reversal. Since everything has to be notched and Mount inside only one way there's not much you can do after the magnet has switched its polarity. On some DC motors they don't have this voltage stud coming in and you can spin the top around but on these  starter motors those wires come in and they are on that side of the can you cannot spin them around changing the top polarity

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Starter magnets loose 16 Jul 2018 09:43 #787053

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 I'm guessing you have nothing to lose, so if you rotate the barrel (effectively the brushes) 180 degrees,  it may start turning in the right direction? 

 It is worth a shot.. If it doesn't work, you have nothing to lose.
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Starter magnets loose 16 Jul 2018 10:29 #787056

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I flipped the top and wiring and rotated it in 10 degree increments until I'd made a 360. No change in direction. A tech said the armature is would for 2 magnets and now there are three poles. Meh, oh well. 

I tried to see about my spare starter on my VN750 and they couldn't be more different if they came from a different manufacturer 

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Starter magnets loose 16 Jul 2018 14:14 #787074

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A gently broken magnet, held together back in its original orientation will act just as it originally did.

Every magnet wants to fly apart into a million pieces. They are held together by the mechanical properties of the material. When a magnet breaks and separates, new poles become apparent where there may not have been any previously, or where the poles may have been different. Depending on how a magnet is broken, it may want to separate. There may be certain breaks that allow the magnet to come back together naturally, but that would have to be planned ahead. Randomly breaking usually results in a weak or strong repulsion of the pieces. But once you mechanically force the magnet back together the way it was, those new poles will be forced back to where they originally were.

This is for when a magnet is merely broken. Now there is the possibility of rearranging the poles of a magnet through high impact. But that can happen even without breaking the magnet (if it's a strong enough material), and is not terribly common on commercially manufactured magnets. You see it more often on things like a screwdriver that has become magnetized inadvertently etc.

Another possibility is if the magnet is affected by a very strong external magnetic force, like another magnet or coil. That can sometimes reverse a magnet.

It looks like it has four brushes. Is there a chance one or more brushes aren't making contact or a wire has broken? Changing the number of functioning brushes might cause a direction reversal.

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Starter magnets loose 16 Jul 2018 16:48 #787081

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So, i fixed it by taking the magnets out of the can and turning them upside down. I had tried at the brush level earlier today and it didn't help. Good now! 
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