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What are the bloody chances ......
https://www.ausmini.com/forums/viewtopic.php?f=2&t=32720		 Page 1 of 2
Author:  sports850 [ Mon Jun 11, 2007 12:39 pm ]
Post subject:  What are the bloody chances ......
The sports850 has been getting sluggish to start , then it lost spark and was sluggish to wind over . I did all the normal things , checked battery , checked points , tried another distributer , checked all the earth points , took the starter out and tried it on the ground , tried another starter in the mini etc etc etc ..... In frustration today I even disconnected the starter while it was still bolted in and earthed it directly to the jumper pack and then hit it with the other lead of the jumper pack and nothing other than building up heat . The motor turns over easy by hand so I grabbed the other starter , put it in and tried it and same deal . Really getting frustrated with it now , dug out yet another starter that spun fairly well but made horrid noises and fitted it , it turns the motor over perfectly and when the little dude wakes from his nap I'll try and start it (exhaust's too loud to try now) . I tried the original starter again out of the car direct to the jumper pack and nothing , tried the other starter I tried and it spins slowly now . What's the bloody chances of having a starter in the car shorting itself out , and the first starter you grab in the shed is doing exactly the same thing :evil: :evil: :evil: , they both worked on the floor first up but wouldn't crank over the motorwhen in the mini and now both won't work . They are now both painted red so I know they need attention and aren't tried again .....
Author:  Wombat [ Mon Jun 11, 2007 12:47 pm ]
Post subject: 
When you're the 'equivalent' age of the starter motor you mightn't 'kickover' as well :wink: :lol:
Author:  Mick [ Mon Jun 11, 2007 12:49 pm ]
Post subject: 
The starter motor torque relies heavily upon the job of the brushes to transfer copious amounts of current into and out of the armature. if the brushes are worn, they have a soft contact and don't do this job very well at all.

If you undo the screws which hold the end of the starter motor together, you will see a set of four brushes. Replace these with a new set (less than 30 dollars) and watch it go.

Running it on the floor doesn't explain too much as the brushes will pass enough current to allow this, but put worn brushes under load and they act more like large resistors.

You might find that the other starter was taken off the car for the same reason.
Author:  sports850 [ Mon Jun 11, 2007 1:03 pm ]
Post subject: 
Yeah , that's next on the agenda Mick , I've never bothered rebuilding starters before as I've got a fair few in reserve but this one has the appropriate date stamped on it ...
Author:  Besser [ Mon Jun 11, 2007 1:06 pm ]
Post subject:  good odds I recon
The odds of haveing a stuffed spare starter increases when the one in your car dies! You get a better one and bolt it in. Then you take the F#$ked one and put it on the shelf and forget about it as your pride and joy is running again.

Next decade the starter plays up and you say...."I've got a spare one here somewhere"

Hey presto you find the original F#$ked started and try to bolt it in.

We need an Ausmini junk bank! for all the dead parts. Then in the "How to" run workshops on getting them operational again.
Author:  Mick [ Mon Jun 11, 2007 1:09 pm ]
Post subject: 
It's pretty easy stuff. The brushes are soldered, so you'll need a pretty decent soldering iron, or one of those little gas ones from Weller or Jaycar.

I used normal everyday 60/40 solder with no problems last time i did this.

Just note the brush placement as they come out, I'm pretty sure mixing the brushes up is the only way to change the rotation of a series wound electric motor!
Author:  Blokeinamoke [ Mon Jun 11, 2007 1:11 pm ]
Post subject: 
Yep mine did that - stuffed bushes. easy to replace - it now spins like a top
Author:  sports850 [ Mon Jun 11, 2007 1:11 pm ]
Post subject: 
It also increases dramatically when you know how many dead mini's we've dragged out of paddocks etc in the last 20 years and stripped for bits ... No idea where the dead spare one came from but at least it wasn't one I'd taken off knowing it had a problem before :D
Author:  drmini in aust [ Mon Jun 11, 2007 2:47 pm ]
Post subject: 
Whilst you're about replacing the brushes check the commutator where they run.
If it's worn get it turned true before fitting the brushes.
When I say true, I mean it- you don't want any runout there or the brushes will lose contact.
Author:  TheMiniMan [ Mon Jun 11, 2007 3:32 pm ]
Post subject: 
I have about 35 more starter motors stacked up here just like yours if you want more of them :-)
Author:  Mike_Byron [ Mon Jun 11, 2007 5:06 pm ]
Post subject: 
Its been years and years since I played with the innards of a starter motor - as well as replacing bushes and brushes, arn't you also supposed to under cut the communtator as well ?????
Author:  9YaTaH [ Mon Jun 11, 2007 5:24 pm ]
Post subject:  Skim the Commie
drmini in aust wrote:
Whilst you're about replacing the brushes check the commutator where they run.
If it's worn get it turned true before fitting the brushes.
When I say true, I mean it- you don't want any runout there or the brushes will lose contact.


True!...they also get a groove thing happening where the brushes have been running for 30 years and the valleys fill with old carbon dust....skim the commie.

As previously advised, auto elecies can also beef the starter up a tad with additional windings :idea:
Author:  drmini in aust [ Mon Jun 11, 2007 5:35 pm ]
Post subject: 
Mike_Byron wrote:
Its been years and years since I played with the innards of a starter motor - as well as replacing bushes and brushes, arn't you also supposed to under cut the communtator as well ?????

Mike,
You undercut the mica on a generator/dynamo. You do NOT do it on starters. I suspect to do with the current flow which is a couple of hundred amps.
Author:  Mike_Byron [ Mon Jun 11, 2007 5:48 pm ]
Post subject: 
Undercutting
Thanks Doc - that clears a loose cobweb in the neurons. I said its been a loooong time.
Author:  Mick [ Mon Jun 11, 2007 5:55 pm ]
Post subject: 
If the mica gets to be level with the surface of the commutator, it acts like a gillette and shaves the carbon brushes down to nothing. The carbon is really soft in comparison to the mica insulator. Any carbon which builds up in the gap that's left gets blown away the second it tries to conduct.

You can do this undercutting your self with a pick and a fine dremel.
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