The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: cbrosolo on 02.03. 2025 08:16
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Hi all, any advice on converting my A10 Big valve 1958 to 12 volt negative earth, I can change globes, ect, but what about magneto/ dynamo, I realise regulator needs to be changed, information would be appreciated ,
Thanks a lot, regards Chris
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Is that positive earth as in your title or negative as in your text?
Anyway i've got one of these on my A10 > https://shop.srmclassicbikes.com/product/electronic-ignition-kit-k2f-twin-magnetos there are other systems available but i don't know. All i know is the one i've got is good. The kit i've linked to doesn't show it but i've got a 12volt reg/rec fitted too.
I've also had the dynamo converted to 12volt.
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Hi Chris,
I converted mine to 12V a few years ago. In addition to bulbs - you have the option to use LED bulbs which takes load off the dynamo.
1. You will need to "Flash the Dynamo" to reverse polarity. Look for instructions here on the Forum or http://www.dynamoregulatorconversions.com/polarising-a-dynamo.php There are many references to this. Quick and easy job. They also supply the DVR2 electronic regulator, which is a step up from the old Regulator. It seems to be a very popular modern regulator.
2. You will be better off to convert the dynamo to 12 Volt which will require new field windings - the 6V ones get a bit hot in Oz. A Forum member here in Newcastle converted my E3L dynamo to 12 volt, and it works well together with the DVR2. The 6V E3L Dynamo will not cut in until the revs are a bit higher.
3. The magneto is entirely independent from the electrical circuit, so nothing required there.
4. Search for LED bulb replacements on the Forum. Some members have found good sources, depending on what you wants the lights to do.
Wait until you get more ideas from the Forum before starting in on it.
Col
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You'll get a fair few replies on this one I reckon Chris!
Nothing very difficult, but some decisions to make, and a few bucks to invest (or more than a few if you go the whole hog).
First off, I'd stick with your magneto unless you really want to go electronic?
For the charging side:
The simpler steps involve:
* choosing a regulator - the DVR2, N for negative version would be most people's choice. About fifty GBP + shipping I think
* repolarising the dynamo by flashing the field (see many posts here for that -No, see Colsbeeza's link!)
* reversing the wiring on the ammeter so the needle moves the right way
* 12v battery and bulbs or LEDs as you say
* some would say replace the horn - but I never have. As long as you don't sit with yer finger on the button for ages, the 6v one will be fine - and louder.
But then you have to decide whether you want to continue with your dynamo as it is, or replace the armature and field coil with a pair of '12v' finer-wound items.
It'll work as it is but will need more revs to cut in and start charging and the field coil gets more of a workout. (As Colsbeeza also just said). If you're out in the sticks and don't have to trickle around in traffic it's not such a hassle and can be mitigated in part by fitting a belt drive conversion which gears the dynamo up a bit. More cost there, not sure how much these days. LEDs help a lot in this case too.
If you want to upgrade the dynamo though, parts are easily available and the job should be do-able for somewhere in the 150-200GBP region + postage, depending on whether you'd be replacing brushes, bearings etc at the same time.
Another approach would be to fit an Alton alternator in place of the dynamo. Straight fit, and regarded (these days if not always in the past) as a good practical option. At a high price though. See https://www.alton-france.com/generators/
So, several ways to skin this cat, all of them work, much depends on what you're going to be doing with the bike really.
Personally, I've continued to run standard dynamos with DVR2 regulators set to 12v, and the combination has served me for well on the various bikes I've got. I've had mechanical failures, but never so far a field coil meltdown. Friends who live in more urban environments, or who tend to do more trickling around prefer to upgrade the windings. And, this being France where they are made, many others use Altons.
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I agree with what groily said on the subject. " 6V E3L Dynamo will not cut in until the revs are a bit higher. "The belt drive conversion will help with this. I have read (can't remember where) That the Alton doesn't deliver much at low revs. I have succsessfully run a 6v E3L at 12v -ve in conjuction with a DVR2 for years without any problems. I also swapped all my conventional lamps for LEDs. You'll be surprised how bright they are and they consume very little current.
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Chris
I fitted an Alton alternator. It is an easy conversion with a belt drive instead of a chain. It works fine and I put the regulator/rectifier under the steering column.
I run a halogen headlight and it copes with no problem.
The only problem I had was that I forgot to check the belt tension and it slacked off and failed. (In Spain) *sad2*
John
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Hi Chris,
I converted mine to 12V a few years ago. In addition to bulbs - you have the option to use LED bulbs which takes load off the dynamo.
1. You will need to "Flash the Dynamo" to reverse polarity. Look for instructions here on the Forum or http://www.dynamoregulatorconversions.com/polarising-a-dynamo.php There are many references to this. Quick and easy job. They also supply the DVR2 electronic regulator, which is a step up from the old Regulator. It seems to be a very popular modern regulator.
2. You will be better off to convert the dynamo to 12 Volt which will require new field windings - the 6V ones get a bit hot in Oz. A Forum member here in Newcastle converted my E3L dynamo to 12 volt, and it works well together with the DVR2. The 6V E3L Dynamo will not cut in until the revs are a bit higher.
3. The magneto is entirely independent from the electrical circuit, so nothing required there.
4. Search for LED bulb replacements on the Forum. Some members have found good sources, depending on what you wants the lights to do.
Wait until you get more ideas from the Forum before starting in on it.
Col
Thanks a lot, great info
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Thanks to all for your input. I think I will stay with the 6v Dynamo and use a 12v regulator, ( I've spent enough money on this bike ). I won't be riding at night anyway, and all my bikes are always on trickle chargers. The only thing that would flatten the battery eventually if on a long run, during daylight, (6v Dynamo) would be the stop light and if it's an LED, it would take days of riding.
So, change regulator, flash field coils, change battery connections and battery and fit 12v LED's, great stuff, thanks everyone. Saluti Chris
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If you don't ride at night, why change from 6V?
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Hi, good point.
I have limited room and the good fortune to have 9 bikes, all on trickle chargers,
it is the only 6volt bike I have, so it always has to go where the 6v trickle charger is, which is a pain in the neck. With the limited room it is a hard shuffle.
Saluti Chris
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Hi, good point.
I have limited room and the good fortune to have 9 bikes, all on trickle chargers,
it is the only 6volt bike I have, so it always has to go where the 6v trickle charger is, which is a pain in the neck. With the limited room it is a hard shuffle.
Saluti Chris
Maybe longer wires would help.
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Given the ease of obtaining 12V bulbs and batteries, I'd always go for 12V where practical.
The dynamo was defunct on m Star Twin and resented being revived, so a 12V field coil and armature were fitted, along with a DVR2. Excellent charging and lights now.
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Job done, converted to 12v , now easier to get globes and trickle chargers, put a 12 volt electronic regulator on it, left dynamo at 6volt and it starts charging around 3200- 3500 RPM, I’m happy , thanks everyone