Stator of a Moto Morini 500 "roasted"

350 Sport & Touring, 500 Sport & Touring
angelo
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Joined: 31 May 2015, 16:34

Stator of a Moto Morini 500 "roasted"

Post by angelo » 31 May 2015, 16:55

My '81Moto Morini 500 made me a "not just" joke !
During a trip of about 200 kilometers among highway and mountain roads, after traveling about 130 km, during a short break, I realized that from the cooling holes of the right case came a large amount of smoke.
The engine ran regularly, it didn't show any change in performance, but the electrical system was completely KO: no energy from the battery.
Back home with the engine working perfectly, I checked the battery (new, FIAMM 30 ha) and it was fully charged.
The main fuse, however, was burned and for this reason the electrical system of the motorcycle didn't receive any electricity.
I removed the flywheel and found the "surprise": four of the five coils for battery charging were literally "roasted".
In many years of experience I have never seen a stator so tatty.
Now I have to rewind the 5 coils for restoring the stator and I'll use wire with a diameter of 0,80mm.
I submit this incident to the attention of those who have the expertise, the time and the desire to make me understand what caused the "not just joke".
Thanks in advance!

350-v-twin
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Re: Stator of a Moto Morini 500 "roasted"

Post by 350-v-twin » 01 Jun 2015, 15:47

Hello Angelo,

I am sorry to hear of your roasted stator. I have never experienced this, and I hope I never will.

But I do have a remark. In the past I have taken out the battery of my 350. When I put it back, by mistake I connected the battery the wrong way: the ++wire on --mass and the --masswire on ++

Immediately smoke came out of the stator and within seconds I disconnected the wires from the battery. Then I re-connected the battery the correct way and there was no further problem. No damage either.

So all I can think of:
a) Did you connect the battery correctly?
b) From the stator, there are 4 or 5 wires coming out: 2x yellow, 1 red, 1 green, (1 white=mass on the newer models). Where they leave the stator, there is a sharp metal edge. Perhaps the sharp edge cut the wire to make mass contact. I normally fixate the wires with an extra tie-rap at the back of the stator to avoid that the wire(s) get cut.

If you like I can add a photo to explain what I mean.

angelo
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Joined: 31 May 2015, 16:34

Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 01 Jun 2015, 16:56

Hi, 350-v-twin.
I start saying my deep thanks for your answer, and here I underline what follows:
a) The battery (brand new) had been connected to the electrical system of the bike from about one week, and it acquitted its job perfectly: Since it was installed, it never presented a malfunction, the electrical system was working perfectly, and (finally) it could provide the energy needed to activate the starter without any problem.
b) from my 500 stator 5 wires come out: two yellow, one red, one white, one green, all of them are contained within a plastic tube.
These wires have a great individual isolation, and the plastic tube that groups them is perfectly isolated from the exit hole from the engine: isn't necessary that you poste a picture: I know very well the problem, and I don't believe that it could have been a case of short circuit produced by one of those output wires from the stator: the plastic tube of my engine is in good working order isolated by a rubber ring.
As additional information, I say that from the time I noticed the smoke and the time I could work on my bike, about 20 hours passed and I found the battery fully charged. If it had been a short circuit, I believe I wouldn't have found it fully charged: it would have a charge below 12,50Volt where I found it.
Yesterday I checked the electrical resistance to ground of the two fastons (of the charge regulator) for the two yellow wires: one of the faston had a resistance of: 16,40 MΩ and the other faston had a resistance of "infinite" (no resistance).
In another charge regulator I've as a spare, the same resistances to ground are 5,80 MΩ for one and 5,10 MΩ for the other one.

350-v-twin
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Re: Stator of a Moto Morini 500 "roasted"

Post by 350-v-twin » 01 Jun 2015, 21:21

angelo wrote:
These wires have a great individual isolation, and the plastic tube that groups them is perfectly isolated from the exit hole from the engine: isn't necessary that you poste a picture: I know very well the problem, and I don't believe that it could have been a case of short circuit produced by one of those output wires from the stator: the plastic tube of my engine is in good working order isolated by a rubber ring.
Hello Angelo, (sorry, forgot to say welcome to the Forum in my previous answer).

But that is NOT what I mean :)

What I do mean: where the wires come out of the stator (at the back). That edge is sharp. Vibration can cause the wire to rubb over the sharp edge and can cause a short-cut.

Image

To avoid this, you should fixate the wire where it comes out of the stator, using a tie-rap. The extra tie-rap is not on the picture.

Please check the back of your stator. Can you show us pictures of the roasted stator (front and back)?

angelo
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Joined: 31 May 2015, 16:34

Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 01 Jun 2015, 23:25

Here I try to post the image of the roasted stator, still mounted in the engine:


Image



I hope the image's size is good

angelo
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Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 01 Jun 2015, 23:39

And here the back side follows:

Image

The little crack in one of the mounting holes is there from about 10 years and it has never given problems

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Re: Stator of a Moto Morini 500 "roasted"

Post by 350-v-twin » 01 Jun 2015, 23:50

Thanks so far, ... looks bad indeed, but please also add a picture of the rear/back side.
On this picture, I do not see the wires coming out of the stator :(

Also, I should use plain/standard screws (M6 x 16) 6mm diameter, 16mm lenght, see the parts catalogue. That way you avoid too much tension in both engine cover and stator.

angelo
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Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 01 Jun 2015, 23:55

I extracted the five wires from the plastic tube that contained them, and their isolation is perfect on all their length. I noticed however that the plastic cap of the faston of the red wire is melted: this is a sign that the excessive electric current, transited through this faston, made overheat the same faston melting its plastic cap.

Image

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Re: Stator of a Moto Morini 500 "roasted"

Post by 350-v-twin » 02 Jun 2015, 00:04

I am still curious for a picture of rear of the stator, a picture like I posted. Size 800~1000 pixels wide please.

Strange part: the red wires feed the transducers. You would expect problems from the yellow wires, as they feed the rectifier/battery.

angelo
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Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 02 Jun 2015, 00:23

here I post a resized image:

Image

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Re: Stator of a Moto Morini 500 "roasted"

Post by 350-v-twin » 02 Jun 2015, 10:52

OK, I am convinced. But I have no explanation of this. Must be a shortcut somewhere in either alternator, or elsewhere.

Tom
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Re: Stator of a Moto Morini 500 "roasted"

Post by Tom » 03 Jun 2015, 10:09

I am not an electrical expert, but what kind of headlamp are you using?
I once bought a bike from which the previous owner thought he could use a 60/65 watt's halogeen lamp, in combination with a 30/35 rear (brake) light and 15 watt's indicator light, this was all wrong since the generator output was only 100 watt's. This action obviously overheated and in the end toasted the generator coils.
I know the 500 output is some 140/150 watt's, but maybe it is a thought to keep in mind.

angelo
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Joined: 31 May 2015, 16:34

Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 03 Jun 2015, 11:16

In my 500 I always use the OEM lamps, I never replaced them with bulbs of higher absorption.
I underline, however, that my stator was toasted during the full day, and the lamps lighted were just the position ones; the high lamps have been off during all that day
I understand your reasoning, but I believe the lamps are powered by the battery, not by the generator: the generator is used just for charging the battery.
If the battery has to supply too much watts for its size, it tends to go to zero volts, and my battery was still fully charged because it was "saved" by the main fuse that I found burned.
Tom, if I understand correctly, did you experience the same incident about the toasted stator?

Tom
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Joined: 26 Mar 2009, 09:23

Re: Stator of a Moto Morini 500 "roasted"

Post by Tom » 03 Jun 2015, 12:12

Yes, but if you have a big battery power 'user' or 'leakage' somewhere, the generator will be constantly 'on' and they tend to overheat, if you do this to long, it will burn out. In your case i should check the earth wiring everywhere(maybe a case of bad earthing on the cable end somewhere) especially at the key/ignition cluster (bad earthing shows in melted plastic cable shoes)...the fact that your fuse holder is melted seems to me as a bad earth connection, maybe the battery charging system is 'on' and 'off' in more extreme's due to this problem and it tends to overheat the generator this way/ has to work harder then normal. Do i make any sence?

Yes i/my brother had a burned out generator twice, once because of the headlight, second because of stripped wiring, but the last incident burned out the coils completely, so that should not be the problem in your case

angelo
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Re: Stator of a Moto Morini 500 "roasted"

Post by angelo » 16 Jul 2015, 23:11

With my great pleasure I inform you that I've been succesful!
Here I post the picture of my "latest masterpiece".
With big patience and with the help of some saints that I called hard several times, I rewound the five stator coils.
I replaced the burned "plastic" supports of the burned coils with the supports of the coils of a stator Vespa.
The OEM supports of the Moto Morini coils are made of a material very similar to bakelite, and those of the Vespa stator are made of hard plastic: this difference of consistency produces some problems of melting of the support when you have to solder the copper wires, but with a little attention I made a good job.
I've to thank all of you who gave me their thoughts and tips, my friend mechanic who gave me a couple of Vespa burned stators, and Gianni of morinispecial.it who showed me where to find the schematic of the Moto Morini stator winding.
This afternoon I finished the work, I went out with my Moto Morini 500 and I have traveled about 15 Km: all right, and the charge regulator works perfectly!
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