Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Bike of the Month Challenge!
1 - 20 of 24 Posts

·
Registered
Joined
·
51 Posts
Discussion Starter · #1 ·
Big problem! My stator has basically melted all the insulation onto the rotor. Any ideas what would have caused this melt down????
 

·
Registered
2022 Triumph Bonneville Street Twin
Joined
·
440 Posts
Possibilities include:

Overload, such as additional lighting exceeding amperage rating of the stator

Dead short on stator wiring
 

·
Registered
Joined
·
4,472 Posts
Hi nhojk1, Short or open in wiring or voltage regulator.

What does bike use for rectifier, regulator?

Stock disc rectifier & zener diode, modern electronic regulator or what?

Has chain rubbed through wire? Can you see melted or heat damaged wires going into wire harness, or in rectifier/ regulator areas or anywhere else?

Can be a fight to remove. Rotor can get glued to stator. Pull both as a unit.

If stator metal poles rubbed rotor it can wipe magnetism out. Melted plastic can be cleaned off, but often not easy.

I’ve only seen two melted. One wire chafed & shorted on frame. Melting stator allowed poles to rub rotor. Both were obviously junk.

The 2nd one Tympanum regulator went open circuit. Stator overheated & partially melted, sagging & put plastic on rotor. Wire to stator & all chassis wiring was good.
New stator, modern regulator (used Lucas brand) cured. I cleaned plastic from rotor, reused rotor. Still working good.

Lots of options for replacement parts. Depends on what you want.

Stuart is expert on this subject. Follow his recommendations. Upgrade to high output 3 phase is wise choice. Requires modern regulator. Unless you are determined to keep all stock, upgrade is the way to go. The Asian Honda type regulator is good plan & doesn’t take much space.
Don
 

·
Registered
Joined
·
8,199 Posts
Also be aware that a failing main bearing will cause the rotor to rub on the stator. Not so likely but it happens. You would have heard a grating sound when running though.
 

·
Super Moderator
Joined
·
8,661 Posts
Hi,
stator has basically melted all the insulation onto the rotor.
(n) Commiserations.

Stuart is expert on this subject.
😌 Kind of Don to say so but I wouldn't call me an expert, I just know a bit.

Overload, such as additional lighting exceeding amperage rating of the stator
Dead short on stator wiring
chain rubbed through wire?
None of these.

The alternator is a generator, it cannot supply more than it supplies.

'Shorting' stator coils is a standard regulation method - Lucas used it before Zener diodes and it's one type of modern regulation.

If the primary chain had cut through the stator wires; the stator's output simply wouldn't reach the rectifier or reg./rec.; no biggie for the stator, wouldn't cause potting to melt.

Possibilities:-

. @rambo Geoff has suggested main bearing failure. However, the clearance between rotor OD and stator ID should be a minimum of 8 thou.; less play than that in the drive-side main bearing would've made a lot of noise ...

. Would be good to know whether the bike has separate rectifier and Zener or a combined reg./rec.?

. Not mentioned so far is the rotor has started to come apart. (n) As originally made, six magnets simply sit on the faces of the centre hex., held in place by the rotor material cast around them. If this cast material breaks away from the centre hex., the hex. starts to push the individual magnets and caps outwards as the rotor is accelerated and decelerated; eventually, one or more magnet caps make contact with the stator ID ...

. Have the rotor and/or stator been dissembled relatively recently? If they have, was the rotor/stator clearance checked all round with the former in different positions?

Hth.

Regards,
 

·
Registered
2022 Triumph Bonneville Street Twin
Joined
·
440 Posts
Stuart, are you stating that it's not possible to overload a generator, AC or DC and thus overheat windings as well as sag voltage?
 

·
Super Moderator
Joined
·
8,661 Posts
Hi,
it's not possible to overload a generator, AC or DC and thus overheat windings as well as sag voltage?
The Lucas "generator" on the OP's bike is an alternator. What is "generated" in the stator windings is AC (most of which ends up rectified in the bike's DC system) and is a function of rotor rotation speed, rotor magnetic strength, distance between rotor magnets and stator coil windings, stator coil wire thickness.

AC Volts across the stator coils vary widely anyway, depending on rotor speed and DC load; given that, "Voltage sag" isn't normally considered.

Potentially, it isn't impossible to "overload" Lucas stator coils but the failure modes are limited:-

. @TR7RVMan Don has mentioned one known already - stator disconnecting from and reconnecting to the rectifier or reg./rec. causes high-Voltage spikes in the stator, rotor spinning fast enough can cause the Voltage to be high enough to break through the stator coil wires' insulation. I suspect this is what you might call "Voltage swell"? From the OP's description of the stator damage, this appears to be less-likely; however, I'd like to see pictures before ruling it out as a potential cause.

. Another power source connecting to the stator could get the coils hot enough to melt the potting; however, the only other power source on a bike is the battery and it's normally separated from the stator by at least the standard rectifier. Standard rectifier, more than one diode would have to fail, and they'd all have to fail closed, and the standard fuse would have to fail to blow ...

Hth.

Regards,
 

·
Registered
2022 Triumph Bonneville Street Twin
Joined
·
440 Posts
Perhaps this link will better explain possible winding failures, as motor winding failures are generally in common with alternator winding failures.

 

·
Registered
Joined
·
8,199 Posts
When my rotor contacted the stator, the main roller bearing had started breaking up. The rollers had lost a bit of surface and was chewing away the outer track. I could hear the grating noise of the stator rubbing so went home slowly . Not an alternator fault but the rotor had a bit of metal missing. That alternator was still usable after the rebuild of the engine.
I doubt this is what caused the failure on the op's bike, it was a noticeable noise.
My rotor and stator seems to last a very long time. Replaced one stator due to the centre getting loose and another had lost magnetism. Never bought new parts as i have original items bought from autojumble.
 

·
Super Moderator
Joined
·
8,661 Posts
Hi,
Perhaps this link will better explain possible winding failures, as motor winding failures are generally in common with alternator winding failures.
Yes and no.

One fundamental difference is in the text under the first image:-
result of an open in one phase of the power supply to the motor.
... Lucas alternators (most motorcycle alternators) are "permanent magnet", there isn't a "power supply" to any permanent-magnet alternator.

Another difference is Lucas 'potted' stators (what the OP mistakenly called, "insulation" that had "melted") specifically to prevent:-
failure ... typically caused by contaminants, abrasion, vibration
As I've posted already, "voltage surge" - caused by the stator disconnecting and the rotor at high rpm - is a possible failure cause but the pictured failure on the windings leaves particular damage on the potting; a I've posted already, OP needs to post images of the damage.

"Phase damage due to unbalanced voltage" is not possible - OP's stator is single-phase.

"Winding damaged due to overload", it is not possible to "overload" a permanent-magnet alternator.

A "locked rotor", the crankshaft can't turn.

Hth.

Regards,
 

·
Registered
2022 Triumph Bonneville Street Twin
Joined
·
440 Posts
In post 6, the possibility of an overload or dead short was dismissed.
The Electrical Apparatus Service Association link included photos of failures:
1. turn to turn
2. shorted coil
3. winding grounded
4. overload

EASA was formed for motor rewind shops to share motor winding and lead connection info and there was no internet when I served on the board of the SoCal chapter in 1980-1981, so I thought it helpful to now be able to share photos.

When I managed an industrial electric motor rewind shop, circa 1979-1983, we were a warranty station for A.O. Smith, Baldor, GE and Toshiba. Coil damage proved or disproved a warranty claim.

If you prefer that I not post in this forum, I will avoid doing so in the future. No point in an Irishman and a Scot arguing.
 

·
Super Moderator
Joined
·
8,661 Posts
Hi,
When I managed an industrial electric motor rewind shop,
In post 6, the possibility of an overload
was dismissed.
'Fraid you fundamentally misunderstand the difference between industrial electric motors and the permanent-magnet alternator fitted to the bike of the thread title:-

. The electric motors pictured in your link, the electricity they use passes through the copper wires in the stator, the magnetic force induced by the electricity turns the rotor.

. On the bike, the rotor is magnetised; at the sub-atomic level, the rotor's magnetic strength induces electron movement in the stator coils, this electron movement being the electricity generated and rectified to supply the bike's electrical consumers - ignition, lighting, etc. including the "additional lighting" you suggested in your post #2:-

Overload, such as additional lighting exceeding amperage rating of the stator
... there is absolutely no way on God's green earth this is possible; while the magnetic strength of the rotor is one criterion affecting the power available to the consumers, the reverse does not exist - the total potential draw of all consumers does not have any connection whatsoever to the magnetic strength of the rotor, nor any of the other criteria that govern the actual power available at any given time.

If the total power drawn by the consumers exceeds that supplied by the alternator, the difference is drawn from the battery. If the battery cannot supply the difference, the lights go dim, the ignition misfires, etc.

To try and be absolutely clear, it is not possible in any way, shape or form for high potential consumer demand actually to "overload" a permanent-magnet alternator.

In post 6, the possibility of [a]
dead short was dismissed.
3. winding grounded
In the same way as the total potential draw of all consumers does not have any connection whatsoever to the magnetic strength of the rotor, nor can there be any increase if the generated electricity happens to find a path to "ground". The fault here is, potentially, stator AC might get into the DC system unrectified. But that cannot cause stator potting to melt.

1. turn to turn
2. shorted coil
There are two ways of regulating alternator AC - series and shunt:-

. Series disconnects the stator coils from the regulator. Causes huge Voltage spikes in the stator coils. Fine if the stator insulation is built for them. Lucas stator insulation isn't, which is why - as I've posted already - a fault disconnecting (and reconnecting) the OP's bike's stator from the rectifier or reg./rec. - mimicking series regulation - might have damaged the stator.

. Shunt 'shorts' the stator coils. As I've posted already, this is how Lucas regulated stator output before Zener diodes, and how modern reg./rec. that can work with Lucas stators work. Shorting a stator coil simply means there won't be any output from the pair and the output from the other two coil pairs (in a single-phase stator standard on the 1974 T140V of the thread title) will be depressed.

. As above, while rotor magnetism induces electron movement in the stator coils, a shorted coil cannot cause the rotor magnetism to induce greater electron movement. In fact, the opposite; the eddy current generated by the shorted coil reduces the rotor's effect on the other stator coils, reducing their output also. That is precisely how Lucas regulation operated pre-Zener.

. Shunt regulation can cause a small amount of extra heat in the stator coils and wires. However, given thousands and thousands of Lucas potted stators have operated reliably with shunting reg./rec. for four decades to my certain knowledge, how can "turn to turn" or "shorted coil" have caused the OP's problem?

If you prefer that I not post in this forum,
:confused: AUP Thou Shalt Nots not contravened, no reason you shouldn't post in this forum?

No point in an Irishman and a Scot arguing.
The thread has reached post #12 without any more input from the OP. (n) Absent that, I'm not sure there's any point in other contributors arguing?

Hth.

Regards,
 

·
Registered
Joined
·
4,472 Posts
Hi Stuart, On the Bonnie I replaced stator & rotor on some years ago, one wire from stator had insulation worn through to ground. So direct short to ground.
The new parts cured problem.
Was it the short the real cause?
If the chain cuts wire, it’s a short to ground while conductor is touching chain. Then open after wire is worn through.
What is the effects to stator?

Ive not seen many 650 with cut wire, but the 3 row chain I’ve seen a few as chain is wider than metal tube.
This is important stuff. Hate to replace stator just to have it fail again! Seen that recently as you know.
Don
 

·
Super Moderator
Joined
·
8,661 Posts
Hi Don,
On the Bonnie I replaced stator & rotor on some years ago, one wire from stator had insulation worn through to ground. So direct short to ground.
Uh-uh. Bear in mind:-

. "ground" is just a random bit of metal;

. single-phase stators don't normally have any connection to "ground", the White/Green wire forms a closed circuit with the stator coils and the Green/Yellow (and Green/Black if present) wire(s);

. so one stator wire conductor making contact with a random bit of metal, how was that random bit of metal connected to the other stator wire conductor? No connection, no circuit.

If the chain cuts wire, it’s a short to ground while conductor is touching chain.
Mmmm ... same as above, "ground" is just a bit of metal; how were the electrons in the cut wire getting to the other stator wire to make a circuit? Even if the cut wire's conductor was making good electrical contact with the chain, there's oil between the chain links, rollers, sprockets, blah; oil's generally a crap electrical conductor (e.g. oil in oil-filled coils still insulates when the HT windings have thousands of Volts).

What is the effects to stator?
Potentially, worst-case, as the chain was wearing through the conductor strands, the connection between stator and rectifier(?) was being opened and closed repeatedly; each time it was opened, that generated a high-Voltage spike in the stator; rotor spinning at a high-enough speed to raise the spike Voltage above what the stator coils' insulation could handle, the insulation might have burned through between two or more stator coil strands. (n) Otoh, in reality, Lucas tested insulation with 110V, so also might not be any "effects"? 🤞

Hth.

Regards,
 

·
Registered
Joined
·
8 Posts
My 6T did the same thing at least 4 times.
First time I thought it was just age so replaced stator and rotor, did not last long
Next time thought it was penalty for buying cheap Chinese copy so I purchased genuine Triumph stator and rotor, assembled them very carefully using feeler gauge to check for correct clearance which was finally achieved by easing the stator mounting bolt holes. Same result so started thinking of possible causes and came up with a theory. I had been experiencing rapid primary chain wear which I attributed to the fact that the typical leaky Triumph primary chain case was causing a dry running chain so started using an oil modifier (Moreys) which seemed solve the chain problem except the lacquer in the Moreys quickly built up on the rotor and/or stator and "glued" them together, Result self destructing alternator components, I changed to "normal" oil and had no further problems. The rapid chain wear was being caused by sprocket mis-alignment due to the pre-unit engine and gearbox being installed in a twisted frame. My problem is not electrical
 

·
Super Moderator
Joined
·
8,661 Posts
Hi,
My 6T did the same thing at least 4 times.
First time I thought it was just age
RM13's and 15's from the late 1950's and early 1960's still 'work' for some people, so they're sixty and more years old. If stator and rotor don't touch, they can't wear.

Apart from physical damage, the usual reason for replacing most older standard Lucas alternators with more-modern is simply the output of the older isn't good enough for 21st century road conditions and legal requirements.

replaced stator and rotor, did not last long
thought it was penalty for buying cheap Chinese copy
purchased genuine Triumph stator and rotor, assembled them very carefully using feeler gauge to check for correct clearance which was finally achieved by easing the stator mounting bolt holes. Same result
"assembled them ... using feeler gauge to check for correct clearance" - I'm hoping you also did this when you fitted the "cheap Chinese copy"? 🤞

"correct clearance which was finally achieved by easing the stator mounting bolt holes" is something I wouldn't ever do. Stator mounting holes have very little clearance to the studs for a sound engineering reason ... any clearance between holes and studs, however "carefully" you think you assembled the stator relative to the rotor, large clearance and subsequent vibration can cause the stator to slide down 'til it's sitting on the tops of the studs, changing the clearance between stator and rotor ... 😖 Last time I looked, a 6T was a 360-degree parallel twin, a cylinder configuration notorious for vibration; on top of that, yours had misaligned primary sprockets ...

Aside, there hasn't ever been a "genuine Triumph stator and rotor", Triumph used electrical equipment by Lucas certainly as far back as the first Speed Twin before WW2.

However, if you bought "Genuine :LOL: Lucas" after 2014, that's just a marketing deal between the Lucas trademark owner and Wassell; with Emgo, Wassell have their stuff made in low-wage countries in the Far East ...

started using an oil modifier (Moreys) which seemed solve the chain problem except the lacquer in the Moreys quickly built up on the rotor and/or stator and "glued" them together, Result self destructing alternator components,
came up with a theory. I had been experiencing rapid primary chain wear
My problem is not electrical
Mmmm ... how does primary chain wear cause multiple alternator failures, unless the chain cuts through the stator wires or hits either stator or rotor? None of which you've mentioned ...?

"the lacquer in the Moreys quickly built up on the rotor and/or stator and "glued" them together" might be the cause of one alternator failure, you might want to consider looking harder for what actually caused certainly the others?

Regards,
 

·
Registered
Joined
·
51 Posts
Discussion Starter · #20 ·
I’ve ordered a new stator and a new oil pump as all the oil has drained from bike since having primary case off , so friend reckoned pump is passing as it the oil should not be flowing through while bike is stood stationary. He recommended I buy a morgo oil pump which I have .
 
1 - 20 of 24 Posts
Top