Electricaly challenged

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Richard Tool

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Hi all - I am now entering the phase of my Commando rebuild that I have only minimal knowledge & skills - the electrics .
I have chosen to stay with standard points/ coil ignition- at least for now.
I made this choice for two reasons - one being that I understand (minimally) it better than electronic ignition and the other being that in the time span of several years and 5k miles it never gave even a hint of trouble . Started very easily and ran beautifully , the only issues being idle when hot and I am blaming that on carb slides . To that end I have purchased a pair of Amal Premiers with the hard anodized slides which I hope will cure that problem.
I still have the original Lucas Zener Diode and bench tested with multi meter on diode test setting - I had resistance across poles in one direction and base reading of 1 in the other - this is the number on display for every function when meter is turned on. In my minimal understanding of this I take this to mean that the diode is functioning properly - however I think it wise to replace it and the rectifier with the solid state Podtronics unit . I have their 6V unit in my ES2 with Lucas MO1L magdyno and it has performed faultlessly for years.
So the first of many questions I am likely to have as I proceed into the dark and mysterious world of electricity is:
Is my original 1972 12 V Lucas RM21 alternator single phase and so consequently I should order the single phase Podtronics regulator/rectifier ?
Next question- I plan on using standard 6V coils/ ballast resistor & condensers.
Does this factor in on the solid state resistor/ rectifier equation and will it be a factor in the future if I install electronic ignition ?

Thanks in advance for any help -RT
 
In my opinion, you are better off keeping your current (original) setup.
Maybe treat yourself to a new rotor, as the magnets will be tired after forty years - but you can tell how much oomph is left by putting your multimeter across the battery terminals and seeing what sort of voltage you are getting at around three thousand RPM (you should see a decent charge at these revs)

To answer your question, yes the RM21 is single phase (two wires)

Your ballast resistor and condensers have bearing on the ignition, and are not related to the charging system.
 
FWIW, I saw no advantage to the podtronics in operation over the OEM Lucas system. In fact, on my bike the Pod produced a couple of tenths of a volt less charging than the Lucas did at the same RPM.

The single phase Pod is what you want with your system but you might consider a switch to the Lucas RM23. But you would then need a Pod 3-phase or a Lucas 3 phase to go with it. The pod is easier because there are no zeners to mount but, again it doesn't work better.

The standard coils/points are fine with a pod. There would be no problem switching to an EI with either the Pod or Lucas. The coils might be an issue depending on the EI. I have had a Trispark for many years that works fine with the two OEM coils but don't know about other EI's

Re EI: Many of the EI's have an advance curve that is not optimum for the bike as far as general use. Many of them do not provide full advance until 5k RPM. That's fine if you are racing and the engine stays at 5k+ all the time but on the street, it means you are giving away response in the area where you most often operate. The advance should be all-in by 3k RPM.

I know most folks will say the OEM points/AAU are a PITA but I never found them to be any trouble. Yes, they require periodic maintenance but it's simple, mechanic 101 stuff and takes very little time in the scheme of Norton maintenance. You DO have to periodically clean/lube the AAU but as long as you do that, there won't be any problems with sticking that is often reported.

One negative about the OEM ignition is that due to the ballast resistor, the charging output of the alternator is lower - on my bike by almost 1V - compared to a TriSpark EI. It's probably similar with other EI's but I have no experience with any other than the TS.
 
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The output from the charging system is the same whether you have the original points or go for electronic ignition.

It’s just that you are warming up the ballast resistor as well as firing your two coils, which consumes more of your amps (you’ve got around ten to play with)

Don’t forget, the factory charging system is matched to the power consumers on your bike, so it’s all good.


I’d consider a modern regulator/rectifier if the zener was broken, because you cannot get a replacement zener very easily anymore.
However, it sounds like yours is still good to go!
The original zener is a nice component, as it uses your z-plate as a nice big heat sink!
Just make sure it’s nice and clean and there is no corrosion around the threads.
 
The single phase Pod is what you want with your system but you might consider a switch to the Lucas RM23. But you would then need a Pod 3-phase or a Lucas 3 phase to go with it.

RM23 is high output single-phase (requires high output single-phase Podtronic reg/rec.).

RM24 (low and high output) is three-phase.
 
Thanks LAB - typo on my part; I had the three-phase, RM 24 which provides more voltage at low RPM than the single phase.

"The output from the charging system is the same whether you have the original points or go for electronic ignition."

Absolutely right, the output is the same but there is less power available for battery charging due to the ballast resistor draw. I checked battery voltage with the OEM ignition and with the Trispark - no other changes. At 1100 RPM with the OEM ignition, (lights off) battery voltage was 12.3-12.4. With the Trispark (lights off) it was 12.8-13.
 
I would not use a Podtronics .Do a little research about this product and the damage it can do to the alternator as it heats the windings of the alternator,there is lots of info on this forum ,of particular note is the work done by Jeandr voltage-regulators.19023/

Paul
 
Your testing of the zener may not be as thorough as needed. it sounds like you just tested it for voltage or current flow one direction and open circuit the other. You need to feed it enough volts or current to where it switches to closed circuit. This should happen by around 13.5 to 14.8 volts. Anymore and it will be overcharging your battery. Mine was overcharging and it murdered my battery after a year and a half. One way test is to rev up while watching a voltmeter on a charged battery. Volts should top out by 14.8 and no more if zener is doing its good work.

As was previously mentioned new zeners are hard to find. I went with a single phase reg rec (Tympanium) and this are good again with original rotor and alternator.
Note you can use a three phase reg rec with a single phase alternator so consider that if you may want to upgrade alt in future. There better for low rpm charging and short trip riding.
 
I made this choice for two reasons - one being that I understand (minimally) it better than electronic ignition

Dont be wary regarding the use and or understanding of EI. There are a ton of information sources to explain how EI works and why it is used in modern day internal combustion engines.

I spent a lifetime cleaning, filing and setting points and replacing condenser's and dealing with coils on a lot of engines....these days I'll take EI over points/condenser every time.

Just one gearheads opinion.
 
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Dont be wary regarding the use and or understanding of EI. There are a ton of information sources to explain how EI works and why it is used in modern day combustible engines.

I spent a lifetime cleaning, filing and setting points and replacing condenser's and dealing with coils on a lot of engines....these days I'll take EI over points/condenser every time.

Just one gearheads opinion.

For me it was the simplicity of EI over points that made my decision. Having zero experience with either and looking at the need to fiddle gaps, AAU. With EI I have none of that and know both plugs are firing off the same circuitry so if there's left to right side differences only need to look to coils, HT cables or plugs.
 
Your testing of the zener may not be as thorough as needed. it sounds like you just tested it for voltage or current flow one direction and open circuit the other.

Thanks Tornado - working on performing this test . I have a variable power supply from my plating operation but I need to purchase a 1k resistor. It seems they come in different wattages - can you advise on which wattage I need ?
Thanks again - RT
 
A car headlamp makes a reasonable load resistor for this purpose. 50-60 watts worth will allow you to test where the zener starts conducting. I think the criteria is voltage at 2 amps. Be sure the zener is bolted to the z-plate for a heatsink.
 
You can get away with cheaper lower wattage resistors by just dunking them in a pail of water while testing. I have used a pair of 20 Watt resistors for many years this way. The water will act like a parallel resistor but has little affect because it is a much higher value than 1 Ohm.
 
I tested my zener on bike with VOM on battery (fully charged) and watched volts as I rev'd up. Found numbers beyond 15-15.6. This corroborated what my SparkBright voltage monitoring led was telling. I foolishly kept riding and one day my battery bloated and died from over charge.
Now i have the typanium reg rec and sparkbright stays at green/good level at higher rpms. Life is good.
 
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Maybe test your Zener as directed in the manual?

Electricaly challenged

That way, you don’t have to fill a bucket with water, or burn anything out with the wrong wattage resistors
 
You can get away with cheaper lower wattage resistors by just dunking them in a pail of water while testing. I have used a pair of 20 Watt resistors for many years this way. The water will act like a parallel resistor but has little affect because it is a much higher value than 1 Ohm.
Russ - maybe next time you are on LBI you can do it for me LOL

I cannot currently test as per manual as I am quite far from lighting up the engine - must bench test.
 
Sorry to offend gtiller with my low wattage resistors in the bucket of water. I was a poor college student when I made mine up. If you have a brain you can do it without burning anything up.
I was mistakenly thinking of the alternator test with the 1 Ohm resistor so never mind / carry on. :oops:
 
A car headlamp makes a reasonable load resistor for this purpose. 50-60 watts worth will allow you to test where the zener starts conducting. I think the criteria is voltage at 2 amps. Be sure the zener is bolted to the z-plate for a heatsink.
Would the Commando headlamp suffice ? or the ballast resistor ? A buddy who is an electrical instructor figures I need a wattage value of 38 in a 1k resistor - does this make sense ? They are a bit on the pricey side - Thanks all for babysitting me - RT
 
Would the Commando headlamp suffice ? or the ballast resistor ? A buddy who is an electrical instructor figures I need a wattage value of 38 in a 1k resistor - does this make sense ? They are a bit on the pricey side - Thanks all for babysitting me - RT

1K is a thousand ohms, not appropriate for this test. Dunno where that value would have come from.

You mentioned having a variable power supply - what voltage range is it? And capable of a couple amps?

The bench test would be to put a resistor in series with the zener and bring voltage up until current is 2 amps. The resistor acts as a current limiter. A headlamp bulb would do the same.

So you're looking for about 14 volts on the zener at 2 amps. You need 2 meters - an ammeter in series and a voltmeter in parallel with the zener. A 50/60 watt headlight would be about 5 amps at 12 volts, 2 amps will be maybe 5 volts. Your power supply must be capable of that plus the zener voltage.
 
Thanks Mylar for the help - my power unit is Hy elec HY1503D 0-15v and 0-3a. My info source for the 1k resistor was found on the internet on Britbike forum - here is copy& paste of page:

"Now if you want to measure what voltage your zener works at you will need about 20 volts and a 1k resistor.

You can buy a 1k resistor quite readily online or at your local component shop. Any power rating will do.

To generate around 20 volts you can wire a couple of batteries in series. Your bike battery will give you 12v for a start. If you have two bikes you have two batteries and 24v.

If not do you have any 9v batteries at home? If you do then connected together you will have 21v for testing.

With 21v and 4 Lucas zeners I measured the following voltages. 13.9, 14.2, 14,27, 14.4.

I hope this helps."

The diode is the original Lucas - would that voltage value be 12v ?
 
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