Is it the alternator?

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Is it the alternator?


Is it the alternator?


Having rebuilt this ramshackle mk2 which has a halogen headlight, the battery seems to be gradually running down, despite me not using the head light often. when it has been on, when not moving (say at traffic lights), the engine will stutter to a stall. all connections have been checked. any feedback will be appreciated.
thanks
ozwald
 

L.A.B.

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It could just be a failing battery? How old is it?

Or...

The alternator stator could be faulty (but check the wires right back to the stator, as the common break point is where they enter the encapsulated stator?

The primary chain can also cut or damage the stator wires if they are too close.

The rotor could have lost some of its magnetism, which will reduce output?

Faulty rectifier?

Faulty Zener diode?

Faulty assimilator unit?


Does it have a Boyer Bransden ignition fitted? As they do tend to be affected by low voltage.
 
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it has a new sparx alternator
new battery, less than 6 months old checked and strong
new rectifier
pazon electronic ignition (which by the way is faultless...very impressed)
primary is belt driven and no damage has been noticed
when i figure out how to put up some photos you can have a look
thanks for the feedback
oz
 

L.A.B.

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15073jrmd said:
it has a new sparx alternator
new battery, less than 6 months old checked and strong
new rectifier
pazon electronic ignition (which by the way is faultless...very impressed)
primary is belt driven and no damage has been noticed

OK, (that would have been useful to know at the start...still never mind) so have you checked the voltage at the battery?



Which Sparx alternator? Single or three-phase?

Which rectifier?


What voltage readings are you getting with the engine running, lights on and lights off?



15073jrmd said:
when i figure out how to put up some photos you can have a look


Link: useful-commando-photo-posting-information-t2357.html
 

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While we are waiting on the answers to Les' questions, when you flipped your fork legs to put the disc rotor on the left side did you stake the bearing lockring so it would not unscrew? Or did you use a Mk3 wheel with the snap ring?

It certainly sounds as if the battery isn't charging. I have heard of issues with Sparx regulator/rectifiers failing. To expound on Les' test questions, test the voltage with the engine off, with the engine idling, and with the engine at about 2500-3000 rpm.
 
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I've had the sputter/stall thing happen at a traffic light stop. Mine turned out to be oxidized connections on the coil. Weak spark. Ran just fine at speed.
 
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Are you running resistor wires, caps and/or plugs? I had a strange situation with my Matchless G12 where I wasn't getting charging from a new high-output SPARX alternator. Took me a while to figure out. Turned out that it was I was running too much resistance in the ignition wires (I had both resistor wire and caps - not sure why!!) and the physical location of the voltage regulator relative to the ignition wires was preventing charging. In layman's terms something like "the regulator was being fooled into putting out a lower voltage and not charging the battery". You should be able to detect this with a voltmeter on the battery. You should need only one of resistor wires, caps or plugs.
 
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daveparry said:
The HT leads have nothing whatsoever to do with the charging circuit tpeever!

I recall reading somewhere that the electrical noise coming from the HT leads can upset some voltage regulators, at any rate, it's worth looking into.

Jean
 

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daveparry said:
The HT leads have nothing whatsoever to do with the charging circuit tpeever!

On the contrary, HT "noise" (RFI) from an unsuppressed ignition system can badly affect microprocessor circuits found in some modern voltage control boxes and digital ignition systems.

Sparx issue this warning:

"**Single & Three phase boxes***
Due to the sensitive nature of both the single and three phase boxes it is VERY important to fit spark plug caps of the 5000ohm resisted type.
Failure to do so will cause overloading."


Digital version ignitions from Boyer, Pazon and Tri-Spark etc. also need 5 kOhm plug caps (or R plugs) to function properly.

Analogue ignitions such as the Boyer Micro MkIII are not affected by RFI.

Running three-phase stator wires too close to an electronic ignition box or its pickup wires has also been known to cause a digital ignition system to malfunction.
 
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I run analog Boyers on all my bikes so the interference from over-resisted ignition wires can affect them as well. I think it's more related to the voltage regulator you are running. It sounds really weird I know but as I said before, it took me while to figure out what was going on. Once I reduced the resistance in the ignition wires to 5 ohms, all was well!!
 
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in response to ron l s question about the forks and front brake, the front end went back on the way it came off. i got the bike pretty much as she is, stripped and cleaned her and put her back together with a lot of help from pete the paint.
new mikuni carb, ignition, coils, suspension, clocks, brakes, clutch, wiring and rear light, sprockets, chain etc etc

she runs beautifully and the gamble was worth it
i was told to sell "the heap of shit and buy a good one"
1300 miles since rebuild about a six weeks ago and i love her
completely unique riding experience ie. light, bags of torque, sporty handling and surprisingly quick, despite the 23 tooth drive sprocket
not man enough to take her past 90 mph
thouroughly besotted
 

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Next opportunity to pull the front wheel, look for a circlip holding the wheel bearing on the non-disc side. If it's there, no worries. If not, then you run the risk of the bearing retainer backing out. It is probably not terribly likely, but Norton warned about this possibility in one of their service notes.

With a 23 tooth sprocket you have a real freeway flyer. I have a 22 on my Interstate and it sure makes a difference over the 19 on my Roadster. Although in a drag race, the Roadster would eat it alive!

Nice work by the way. There's a real sense of satisfaction bringing one of these back from the dead.
 

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Ron L said:
Next opportunity to pull the front wheel, look for a circlip holding the wheel bearing on the non-disc side. If it's there, no worries. If not, then you run the risk of the bearing retainer backing out. It is probably not terribly likely, but Norton warned about this possibility in one of their service notes.

The front wheel appears to be laced in the pre-MkIII spoke pattern, so it probably is the pre-MkIII hub/wheel?

MkIII 'circlip' hubs can be identified by the groove on the hub face opposite the disc, see photo:

Is it the alternator?


The pre-MkIII hubs with threaded retainers do not have the groove. http://www.oldbritts.com/image/wbui_b.jpg
 
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Is the initial question of this thread still an issue? engine cutting out at lights etc....Do you have a test meter?
 
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Hope its OK to resurrect this thread to try and glean the benefit of the collective experience.

I have a ’72 750 fitted with a Lucas 3 phase high output alternator setup – RM 24 alternator & Podtronics voltage regulator/recticifier. I seem to be suffering from low alternator output. Although I can ride several hundred miles with no problem as long as the lights are off, within a few miles of switching the lights the ‘bike starts to misfire (Boyer ignition). With the lights on and engine running the best reading I get is 13.25v and that is about 2000 rpm. It may even be dropping as the speed rises. Swapping the regulator for the spare I take on holiday makes no difference.

Using a nominal 1 ohm resister (measured at 1.4 ohms when in circuit) gives 4.5 v across any two sets of wires (3 wire type alternator). By my reckoning that would be, at best, a total of 60 watts output. I have swapped the rotor but get almost identical readings.

The £75.00 question is – is my stator gubbed? If yes, is the opinion to replace both the stator and rotor as unit?

Thanks in advance.
David
 
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