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Issues with alternator

I’ve recently bought a 961 commando and I love it! Unfortunately though it keeps letting me down, the battery is fully charged when I leave home but when I arrive at my destination, how ever short the journey might be, the bike then won’t start due to lack of power. I’ve been told that it’s probably the alternator or rectifier, but neither are my field of expertise. I would appreciate any advice or any recommendations for an electrics specialist, I am in Sussex. Thanks


More likely to get a suitable reply if this question is asked under 'Donington Nortons' and/or 'Electrical'.


My new 961 did almost the same thing. It broke down on day 3 of ownership. After being returned from the factory, unless taken on a long run each week or kept on a trickle-charge. the battery would be too weak to start the bike.  A call to Factory was made and I was told to keep the bike on a trickle charger 24/7 when not ridden regularly.

Even this failed to help as twice I took the bike out of the garage, started the engine and left it idling while I closed the garage doors. Securing these doors took around 30 seconds during which time I could hear the 961 engine wind down from a fast idle to stalling. Then it would not re-start due the battery having gone flat. This was due to all the gear pulling juice from the battery when the motor was idling. This included the 55W filament headlight, the Ignition coils, the ECU and other electrical hardware. When I put a meter across the battery circuit, 8A of current was showing being drawn with an idling engine.  The bad meter news continued as when the ignition was switched off, 150mAh was still disappearing due to the sensors, alarm and ECU remaining active.

I met several owners with the same problem. One mentioned  a slow drive across London as being fatal. The engine cutting out after braking and then refusing to restart.  Another owner had driven up north, stayed overnight at a B&B, only to find a flat battery the next morning. I lost confidence in riding the bike any distance and sold it asap.


having followed 961 owners on the web, this is not a particularly common problem. Other elec gremlins do occur, particularly on certain years of production, mainly due to different versions of components fitted. Suggest getting elc. charging system checked by competent technician, with and without engine running etc. ( I always keep mine (2018 model) on trickle, and no similar symptoms so far.)

    Do you know if battery condition is OK as first test??

Thank you very much for you input ,! I’ll just have to find  auto electrician with enormous patience .the shame is the bikes go well and look great all the best to you Philip

In reply to by jan_nelder


Hi Jan, I’m pretty sure the battery is fine and keeping on a trickle charge doesn’t seem to make any difference sadly. I’ll just have to find an electrics specialist in the hope they can help. I really love the bike so I’m hoping it can get sorted, thanks for your input, happy to know that the problem may be rare.


I have a 2017 961, first year all was good then in the second year the battery failed (red light on my optimser. Battery was replaced by Norton but not under warranty. Last year started having issues with starting again, was getting a gamble on whether it started or not, sometimes it would attempt to turn over and other times would just click.

I keep the battery connected to an optimiser and according to the displays all is good but the bike seems to know better, still a gamble. Also i have an intermittant issue where the tickover races away and the only cure is to pull up and switch off and on which then brings the issue of it starting again.

This was my dream bike to go alongside my MK3, its a beautiful bike and really turns heads but im now at the point where i have to say enough is enough and let it go, a bike needs to look good and be relaible.

Whilst in the Donington workshop in 2019 i couldnt help but notice a tray of 961 batteries all marked as scrap, tells me im not alone with this issue. Personally i think the battery is borderline capable of turning over the big parallel twin.

I wish there was an answer.

Kind regards,




My experience was similar to Ian. I was finding a flat battery if the bike was not run or charged each week. I contacted the Factory who recommended an Optimizer or similar be connected every night. This worked fine for around 3 months until one morning the bike just went clunk when the start button was pushed. Another call to the Factory and their suggestion was a replacement battery at my own expense. The replacement battery faired no better and not long after my trickle charger was unable to keep up with the discharge rate. I asked the Factory if I could fit an on-off switch into the battery circuit and was told 'no because the onboard computer would then lose all of its settings.' Was it not doing this anyway each time the battery went flat? 


You should receive your February Roadholder in a day or two and on the rear page is a new contact email address for the (modern) Norton technical helpline. It might be worth trying that. Norton are now keen to work with the Club.


Would someone please move this thread to the correct forum.

Best regards 

Katherine Scott

Confused about the Factory advising "onboard computer" (ECU) losing settings if on-off switch fitted into battery circuit. When changing the battery on my 961 the circuit is disconnected anyway and then when starting up again with new battery fitted nothing changes , ie , starts and runs just fine, as before. Perhaps the ECU has a memory that withstands main battery disconnection ? 


Hi James,

Maybe the ECU has a supercap or battery within itself to keep the memory for a short while, only the factory will be able to confirm this. Just a thought from my experience within the CNC industry where i come across this all the time.

Kind regards,



Why not try the Access Norton forum, there's a wealth of informed advice about the 961 including folk who understand how the ECU works.  There are certainly threads about parasitic current drain, which can happen on any vehicle, and info about different batteries for improved starting.  I believe some speedometers were found to cause a current drain on the 961.

However, if you are losing charge on a short run then I would look at the battery first, as someone has already mentioned.  Just because it’s on a trickle charger doesn’t mean that it’s ok.  Do you know that it's holding its charge?  Have you tried charging it, taking a reading, leaving it for a day and then taking another reading?

I've had my 961 for nearly 8 years with the original battery which still works fine.  I disconnect it over the winter and charge it once each month when I'm not using it.


About the 961 PCM, but as a former Calibration Engineer in the motor industry,  I know most cars have a 'keep alive memory' within the PCM that draws around 10mA current from the car battery. Can only assume that the Norton PCM is similar.

At that rate, a fully charged 20Ah battery would be flat in around 3 months, so it makes me wonder if there is anything else that is being 'kept alive' on the bike. (e.g. ABS?) How many other 'modules' are there on the bikes? 

I do wonder how large the 'learning' area is, and how far/long you need to ride to relearn. (I know it will continuously learn almost all the time you ride it as long as the engine is hot). If this area is small, as James suggests a master battery switch could well be a good idea.


There was more than one make of ECU (SCC and Omex) depending on when your 961 was built.  The SCC ECU is more accessible than the Omex and some folks on the Access Norton forum have reprogrammed theirs using software that is available from the supplier, having had the supplier unlock the ECU.  Even if you don't change anything it's useful to have the software to see what's going on.  I've included a couple of screen shots from when I had it hooked up to my bike.

A few years ago I asked SCC whether any settings were learnt and retained in the ECU and their reply was "Aside from referencing the stepper motor for idle control on each switch off, no."

There is also information on Access Norton about fitting a battery isolation switch, and tracing parasitic battery drain (which should ideally be around 1ma).


Why don't they store the factory settings in CMOS backed up by button cell? My computer doesn't forget its BIOS settings every time I switch it off.

PS Please ignore this!



Assuming it is a 5Ah (or more) Li-Ion battery it should give you 8A for 35 mins, or if the alternator gives 4A on tickover 70 mins (in theory).

Test the battery's capacity - I use a 35W/12V dichroic lamp on a GU5.3 flying bulb holder. 3A draw, should last at least 1.5 hours. A few quid. eBay 233458736662.

I had a Li-ion battery with severely reduced capacity which had plenty of volts, so it seemed OK.

If you jump start a Li-ion battery from a lead acid battery you will fritz it. Don't ask me how I know.

If you really want to see what's happening get a digital 100A shunt at about £12 eBay 313174267960. Works on a 9V PP9 battery.



Not sure what you mean by the "factory settings".  The ECU is programmed with a map containing the base settings for the 961, it doesn't forget this information.  While the bike is running the ECU will then make adjustments in real-time based on input from the various sensors, such as the head temperature, barometric pressure, throttle position etc etc. with reference to the 961 maps in the ECU.


A solid state switched mode charger which is not specifically designed for Li-ion will fry them too. Apparently old fashioned heavy transformer/rectifier types work OK, but are not ideal.



........jump start without ruining the battery.

That's not the case for a 961, which is what this thread is about.  Someone has simply pointed out that you shouldn't jump start a lithium-ion battery using a lead acid battery.  The 961 factory fitted battery was lead acid.  Some folk have swapped them out for lithium-ion with mixed results.


The 961 needs a big voltage to ensure easy starting. My bike has eaten standard batteries for fun. Changed to the lightweight more expensive Jap shori ones no problems for 3 years.


I don't own a 961 and never will (Between you and me I probably wouldn't have one as a gift!) but, assuming it's electric start, you want a battery with the highest cranking amps you can fit - preferably 20Ah or more if possible. (Big Amps Dave, not voltage!) Current drain can be assessed with a multi-meter or volt meter by removing the earth lead, setting the meter to the 10A DC range and putting the lead in series with the earth lead and battery "Earth", when nothing is switched on.

From the reading you get you can calculate how long your battery will last without charge.  Bear in mind that a lead-acid battery shouldn't go below 50% of its capacity. I would hope that the electronics would have an EPROM so that essential settings are "remembered" when the battery is disconnected or switched off if you add a switch to the circuit.  Hopefully the factory will have the maximum drain current listed so you will know if something isn't right.

I'm surprised that people are using Lithium-Ion batteries as they need different charging characteristics to Lead-acid. They also don't have a very good shelf or operational life - about 3 years they reckon.

I have had similar problems with my car so I keep a smart charger connected now that it's SORN'd.


I was assuming that everyone knows how to test a battery but in case not, here's some advice.

Disconnect the battery, check the voltage, put it on charge using the charger of your choice.  (Each time you check the voltage make a note of it.) A "smart/intelligent" charger should tell you when it's "Full".  Switch off and disconnect the charger and check the voltage.  Leave it an hour or longer - then check the voltage again.  Leave it even longer, if you have the time (a day would be good) and check the voltage again.  For a 12V L-A battery, it should not be below about 12.4V. - that would indicate 80% charge.  The higher the better. 

If there is a steady voltage drop over time it means that the battery isn't holding it's charge and may be u/s.  Keeping it connected to an intelligent charger may resurrect it.

If all is well then reconnect it to the bike, start it up with nothing switched on and check the voltage at the battery terminals.  It should not be less than 13.5V on a lead-acid, preferably over 14V.  If it doesn't reach this, then the alternator system is inadequate.  It would be best if this was in a garage as temperature affects everything - you need a higher float charge as the temperature goes down.  Check it on Google.

A Li-ion battery is a whole different ball game!


I have had this all over the years. People on the different web sites telling me what a load of junk the rotaries are when they have never ridden them and don't even know how they work. I sold my Rotary with 113 K on the clock and  NOT ONCE did it break down on me in ten tears of ownership.  The  'website wooden tops' as I call them know the price of everything but the value of nothing , and over time I have come to forgive these unfortunate people for they are severly  misguided individuals who think they know everything, having read every comment back to front and made a decision on just the written words of other people.

I love ALL Nortons especially  Commandos and ES2's and if you read 'Roadholder' all the different models have problems, and have had since new but the owners are more than happy to forgive and forget their little foibles all in the name of love of the brand.

I bought my 961 six years ago and love the thing to pieces and have already forgiven it for a few niggles it's thrown up, but I will never sell it  no matter what the nay sayers say. Believe me it's a great bike with a great name on the tank and I made my own mind up to buy one, and I am glad I didn't listen to the moaners and so called experts out there.

After many years of experience you'll find that there are differing opinions about everything on this planet.  With any item you can think of, there may be those who claim it's the best thing since sliced bread and others saying it's pile of poo!  The opinions will often be moderated by the user's personal experience (or should be if it is negative criticism).

Those who have had experience of something are, of course, entitled to say what they think of it and your pleasant experience of the 961 is definitely not the same as some others.  The old saying "One man's meat..." is very apt and no-one should be offended if someone else's opinion of their pride and joy is perhaps the opposite of their own.

Nothing and no-one is above criticism, as long as it is reasonably polite!  As an example, any over-sensitive members who disliked my comment about not having a 961 as a gift, need to be aware of my own circumstances - it was a jocular comment anyway!

First; I am nearly 75 with Osteo-arthritis so would probably not even be able to SIT on a 961, let alone ride one!  Second; my interests are almost solely in OLD British bikes, Nortons in particular.   I have no interest in "modern" bikes, which would be anything from about 1980 onwards.  So I'm not a "real" biker - very blinkered tastes.  I have had more mechanical experience with cars; Jaguars in particular since buying my first in 1971.  I could probably disassemble an XK Series straight 6 engine blindfolded, arthritis permitting.  (Reassembling would produce several surplus parts of course.)

This all means that "moaners" may well be justified in having something to moan about in light of their personal unfortunate experiences.



As its a discharge concern whilst actually on the move, I'd check the connector block into the reg/rec, make sure that is plugged all the way home, as they've been known to come unplugged before. Then check the charge rate at the battery, assuming the battery connections are all sound you could do this at the starter motor for an initial test, just for ease. After that, and if no other fault found, get the battery load/drop tested.


Here is a silly idea about your problem:

Since the problem only occurs when you are riding the bike I would suggest that you check the wiring under the seat.  You might be pinching a wire when the seat is compressed.

In the same regard, the wires might be getting pinched when the suspension is compressed, i.e. around the rear shocks.

Hope this helps



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