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ES2 stator failure


Following from my earlier post sadly my stator has self destructed, so a bit of background before the questions.

I have only had the bike a couple of months, the ammeter had received a bang before it arrived and the chrome ring and glass are missing (i am replacing it), but it seems to function. But when the bike is running the ammeter oscillates over a wide range, with the average making sense relative to load/revs. At constant speed it eventually settles down but as soon as the revs change or elec load changes away it goes again. Having looked closer the stator is a 47205 (2 wire, 12V 120W) and the rotor a 54202298. It has an electronic regulator/rectifier and also has a Boyer mounted direct on the end of the cam wheel which would normally drive the timing chain.

I had only done short runs, mostly around town, but last weekend did a 100 mile open road run. It smelt a bit hot on return, had coughed once at speed but otherwise ran well.

Have now found the stator has melted on both edges. I was careful regarding clearance when i reinstalled, and it doesn't seem to have rubbed, but it could have been my poor set up.

I have a spare matching stator and 54212006 rotor, but before mounting those would be interested in any feedback on whether the oscillating ammeter is possibly a reflection of rectifier issues and if so could that cause the melt down? Or are there other possible reasons for a melt down, rather than just my mechanical incompetence.

I have a 4 day ride leaving on Friday and don't want to fry things again half way through the trip.


Hi Iain,

Not sure if this really helps but my Electra and Navigator both have the oscillating ammeter you describe, I always put it down tosympatheticvibration. If you can, try putting a digital meter in in place of the analogue, you should then see a sensible reading.

When you say the stator is melted on both sides, where exactly do you mean ? could you attach a picture ?





sorry for the slow response, have tried to attached a pic, hope that works.

Both sides - a track has been melted around the circumference and near each edge of the stator.

I have now mounted the spare unit (ex Commando), clearance rotor to stator definitely ok, a short run suggests it is heading the same way.Alarge dropof light brown melted goo below the alt. Less swing on the ammeter with the new Alt but it was reading around 6 Amps charge at 30mph, ona charged battery. The wiring is not stock, at least 4 fuses i have found so far - time to sit and plot out the diagram, check connections, bare wiresetc.

Measured around 13.5V across the battery when reved up.

Attachments Melted-Alt-001-web.jpg

Hi Iain,

It is very strange that the stator is showing signs of cooking but it also appears to be charging the battery. I think you are going in the right direction with a 'check everything' approach.

Maybe Al Os has an idea ? I know he does look at the forum but it may be worth emailing him with the picture at




Al OZ here! Sorry can't offer a reason for melting stator at this time nor distance. But the oscillating ammeter I wouldn't worry about, they all do that! It is pure vibration and a cheap meter. One way to stop it is to fill the ammeter with some thin clear oil. 3:1 is about right. I did this years ago and it damped the meter fantastically. Eventually the ammeter sprung a leak and the oil ran out, (not that it noticed on the Norton!) But the residue of the oil still helped to make ammeter readings quite useful.

Now the melting stator. The only melting I have ever seen has been down to a rotor stator gap being interference! This burns out the rotor/stator very quickly, can even cause a seizure of the parts hence engine! But for very many years the only overheating was this contact. I have never known any electrical loading causing them to over heat. Although the higher output alternators do bear some burn marks after some mileage.

I would say that if your battery is charging at 6 amps then this is too much, but I would think it is an optimistic! reading. Use a decent meter to confirm when you can if you are bothered. But as long as the battery voltage never gets above 15V and you don't blow bulbs and you don't loose battery acid then all is correct.

Melting stator-now a GUESS is that I wonder if the stators you are using are of recent-foreign manufacture? As we never used to have such problems.

Now your wiring-4 fuses? why? perhaps there is faults in various parts that haven't been found? I had a MKIII with this syndrome recently. Other persons fit many fuses, Al Oz found the real fault-put it right and returned to a single fuse on a Norton which is quite adequate. Seems yet another bike needs a rewire! After monkeys have been at it.



Thank you both for the feedback. Life has been a bit hectic of late so i have made little progress since last posting.

I replaced the rotor and stator after the first melt. The spares came out of my Commando 5 years or so back (it now has a 3 phase) and were on that bike when i bought it in 1984 so not too recent if they weren't original.

From your comments Al it could just have been a clearance issue - i did take care to set it but the cap srews that held the stator in place are a very loose fit in the 12V stator so rely on friction under the washer to hold the location. I have since picked up some studs but these must be correct for the 6V stator and still need sleeves to make sure nothing slips on the 12V. Will do that before trying again.

On the fuses, two by the battery - 20A main and 5A on a feed to the electronic ignition. Two more in the headlamp shell which I haven't figured out yet. I will get to the bottom of all that too before getting mobile again.

thanks again



My Atlas motor once showed signs of an overheated stator and possible contact with the rotor. I was surprised as the stator was properly mounted on studs and had been accurately located. However, I concluded that the stator must have vibrated out of position. I made a mistake then as I did not check the gaps before undoing the stator. I carefully refitted it and all appeared well. Some considerable number of miles later, at full throttle, accelerating in 3rd gear, uphill, the crank broke across the drive side cheek. I believe that the crank was already failing when the stator problem showed up and if I had checked and thought more carefully, I might have avoided a wrecked engine. I should add that the engine was an ex race motor and the crank was lightened and rebalanced. By the way, I don't believe that your ES2 crank is about to break! It won't be flexing quite the way a twin's crank can when pushed.




I would be very suspicious of your regulator/voltage control box. Al does a good cheap replacement. The charge rate does seem excessive. Also, I suspect there may be a hidden intermittent short circuit. That would explaing both the oscillating ammeter and the high charge rate (current running to earth). And the extra fuses. And possibly the cooked stator if you are quite sure the air gap between the rotor and stator are correct.


P.S. I might have an Atlas crank on the shelf...



Looking at that stator, and if you checked the clearance when you fitted it, I would check your main bearings! Get hold off the end of the crankshaft and give it a good yank up & down. If there is any hint of a knock then they're knackered!




Even the 180W stator with all the wires shorted out won't create enough heat to burn your stator like that. I'm afraid it's down to "pilot error" on behalf of the builder. If you don't find an Atlas stator we have 17 good used ones in stock and four new ones. Les Emery


One thing I should add to the above text is that the crankshaft must be turned to many different positions when checking rotor to stator gap. This is just in case the alternator side of the crankshaft is slightly bent. Don't use any rotor if the number on itends in 2006, these are exploding ones. Les Emery


Thanks for the feedback, life has been hectic so haven't fully sorted things yet, but "pilot error"

may well be it.

Les - thanks for the reminder on the 2006 number, will get rid of that one.


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