Honda CG125 1982 6v to 12v conversion

[Thoney]

HI all,

I have recently bought a 1982 Honda CG125 which has a 6V Battery, I want to do the conversion to 12V and It will be my first battery conversion, I was wondering if anyone could help me on this or put me in the right direction to someone who could?

thanks!!

[Teflon-Mike]

Search engine is your freind, this ghas been covered on a few occassions.

First question WHY do you wish to convert from 6v to 12v?

The electrics on little bikes tend to be pretty 'weak' regardless, and having more volts wont give you more 'power' to run such equipment as a higher wattage head-lamp or the charger for a GPS or smart-phone or anything.

Main advantages of converting an old bike to 12v is for 'compatability' 12v bulbs and stuff tend to be easier to come by and are often cheaper.... Though that's possibly something of a 'non-problem' with e-bay and so much now only a couple of clicks and a 2-day DHL jiffy-bag away... especially as you have so little electrical shit on an old bike to need many parts, and if it's in half decent shape to start with, shouldn't need much very often.....

Though living through the 6v electric and AC direct lighting era, I would reccomend buying a couple of headlamp bulbs and 1/4 dozen tails to keep in the tail, as they do seem to like to pop pretty readily.... more so if you try fitting higher wattage ones than the book says.

Other advantage is 'reliability'.. which most often translates as being able to neglect the maintenance....

12v electrics have twice the electrical 'pressure' between the battery terminals, so when you have a cruddy corroded up old switch or bullet connector or earth point, electric has more 'force' to push through the high resistance it offers.

BUT, 12v isn't the 'solution' to that problem... the solution is to clean the contacts in the switches or in the bullet connectors or earth points, to get rid of the corrosion making them high resistance, and to make sure the rubber insulation around them letting moisture in, is 'good' and giving them all a good dosing of WD40 used for its intended purpose as a 'water-dispersant', to keep it at bay, and let the electric get through under the pressure it has at 6v as it should.

If you try and ignore that 'root-cause', then even if you convert to 12v, the problem will still be there, and switches and contacts will remain a 'bit iffy' and unreliable.

Most oft suggested reason for wanting to go 12v though is for better lights..... which a 12v conversion on its own will NOT offer.

Brightness of a headlamp bulb is dependant on the power rating, the wattage. so if you want to fit a brighter, higher wattage headlamp bulb, you need more POWER to make it light, not just more volts.

Generator only chucks out so much electric 'power', so if you want to use more for the headlamp, then you need a generator that will deliver it..... find it else where.... sharing out what you got less equally to give the lamp the lion share.

Little bikes like the CG, though don't have very much electrical equipment, and certainly noting that's likely to be drawing many amps at the same time as the head-lamp all that often, you can steal watts from..... say fitting lower wattage indicator bulbs or even lower LED indicator bulbs to free up some amps for the head-lamp.

Other issue with the 6v CG and even most of the 12v ones, is that they have AC-direct head-lamps; they are powered directly of unrectified, unregulated electric straight from the generator... they are only notionally rated at 6v, the generator delivering a varying voltage 'wave' with peak's of anything from 6 to maybe 16v depending on the engine revs.

It's actually a very 'efficient' little system... it's just not very powerful!

And trying to convert to 12v regulated DC current taken from the generator through a regulator/rectifier to a battery to stabilise it at a constant 12v, can actually see you get less from it, depending how its done.

Standard 6v system, where it takes electric from the generator to charge your 6v battery, to charge the battery, actually uses a very crude 'half wave' rectifier called a zenner diode. This lets +volts through but blocks -Volts, so it only takes the positive hump of the wave supplied by the generator, about half the 'power' the generator may be making....

Using a more sophisticated 'full-wave' rectifier that uses four diodes in a bridge circuit, so that the out-put pins get positive volts, regardless of which way the input is pointing, will get you more of the power the generator is making, less an efficiency loss AC direct to the head-lamps just doesn't have....

Is possible though to use a now, reasonably 'cheap' four or five 'pin' 12v rectifier to charge a 12v battery off a notionally 6v generator..... remember, that AC generator will deliver anything from perhaps 3-4v at a lumpty tick-over up to perhaps 14-16v when revved....

BUT you will never get more power OUT than the genny can put IN, so you will still have a limited number of watts to point at a head-lamp, and if you want to run anything more than the stock 35W or so bulb, you will probably still be struggling.

I have done it to an old, small, points ignition Yamaha engine, using a £10 four-pin Pit-Bike regulator, using the 'standard' 6v generator.... BUT still didn't have the 'power' to light up anything more than the standard 35w head-lamp bulb.....

& it was FAR from a cheap or easy conversion, after buying all new 12v equipment, from the battery through to the horn and all the little bulbs behind the speedo, as well as indicators and indicator flasher etc etc.

I also 'robbed' a lot of watts from that equipment using a chrystal times transistorised 'electronic' indicator flasher to be able to use LED indicator bulbs without loosing the benefit of thier low wattage, using 'ballast resistors' to load them back up the same as a conventional bulb to make them flash at the right rate.....

And the initiative for 12v conversion wasn't to get better lights, as to be able to run a GPS (as opposed to Sat-Nav) for Green-Lane orienteering on the thing.

With 12v on the bike, though did allow me to tackle the head-lamp issue with a more efficient HID head-lamp, that's about 10x as bright as a tungsten bulb for about half the watts, and only draws 35, the same as stock 6v....

BUT, whilst that is about as good as you can get, and conveniently with limited electrical power.... it's another convoluted conversion; and to use an HID you need to have a head-lamp which will take an available HID bulb fitment.... 6v bayonet bulbs tend not to be compatible, begging a more modern 'H' type fitment for 12v halogen bulbs. Depending on the HID arrangement, you may also need to use a 'corrected' HID bulb to get it to dip properly, and or an HID compatible lens/reflector in the head-lamp.... all of which to do the job properly, as in it actually works, and works as it should and better still doesn't annoy the MOT man, tends to preclude the cheaper 'systems' found on e-bay... of which the cheapest are only HID on 'full-beam' and have a tungsten element for dip, which used most, means they afren't actually all that much of a bonus very often!

HOWEVER... cutting through all of them permutations in the 'plan'.....

Back to basics.... and old rule of proddy racing, before looking for MORE than 'standard' make sure you have all you should AS standard......

IF you tackle a 6v system at source; and do all the basic grunt niggly neglected maintenance, and spend time cleaning contacts and corrosion, replacing wires that have gone black and horrible and the insulation started to go hard and crumbly, and get the full 6v flowing round the system as it ought to... replacing previouse owners 'ideas' that a 45w bulb MUST be brighter than a standard 25W one, and making sure that the tail lamp is actually a 6v one, and rated at wattages in the book, and not a 12v car tail lamp bulb bought at a petrol station and chucked in as a get-me home fix at some point, and never changed, cos it never blew again.....

Tackling the issues at source... you are likely to get as much or more from the 6v system than you would trying to bastardise it with a 'modernisation'...

Like I said, these days availability of even relatively uncommon components is so good it is far from the issue it was in years past; whilst making the wires good and getting all the volts you got through them will eradicate more intermittent and or annoying electrical issues than upping the volts...

AND that head-lamp.. with the correct bulb in it, getting all teh volts it shouls, will deliver a lot more light.....

And if THAT isn't enough.... look at the lens and the reflector!

Usually on older bikes tarnished in the reflector that has probably lost a lot of its silvering so is probably not chucking half the light the bulb makes at the lens, which old yellowed and etched with however many years of grime, probably doesn't let half of it through anyway!

Up-rate the electrics and lamps as much as you like.... but with cruddy old lamp unit, only letting 1/4 of it out, you'll need 4x as powerful a bulb, JUST to get as much as you should have!

Exhaustive effing about with bike lamps over the years, has proved to me, that if the lamp's 'weak' to look at the lamp, not the bulb, and clean or replace the damn thing, depending on how dire it is.

And new, good quality, not after-market patern get me through an MOT bit of shit (of which I have more than I would like cluttering up the shed!!!) will give you far more of what you really want, and far more easily than trying to get clever with an 'upgrade' or mod. likely to make more problems than it solves!

KISS IT.. Keep It Simple - keep it STADARD.... its a good moto...

If you have to go away from standard, make sure the reasons are sound, and the plan to do it 'reasonable' and with a better than good chance of actually delivering what you hope it will.

CG, is enticing in later models, and Chinese derivatives having 12v electrical systems, and suggestion that pillaging parts from an MOT failed chink 'might' offer cheap and easy convcersion...

It does... but reality is that there are enough differences in the systems to make it a mine field, where you ARE likely to make more problems than you solve.

Which brings me back to the top... and WHY do you want to convert to 12v?

An un-molested 6v CG retains the virtues of simplicity; trying to bastardise that, and fit some sort of hybridises electrical system on it, that isn't anything like the Paynes Manual depicts, could be chucking the baby out with the bath-water.....

you could get more of what you actually hope for simply overhauling the 6v system and making sure you have all you should as standard.

And avoiding the 'problem' of not being able to charge your smart 'phone on it, by not being a slave to it every time it bongs with a twitter tweet or whatever, and using a far more reliable way of navigating than its Sat-Nav-Ap... called paper MAPS, and street-signs and such! Worked for a century before Smart-Phones came along!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[smallfrowne]

I fitted a CDI stator to mine, along with a matching cdi and ignition coil. The genny cover no longer fits as it won't go over the new pick up for the cdi, so got a CDI genny cover for it too. 12v rectifier in place of the resistor that lives on the lower fork yoke. You'll need a 4 wire rectifier if I remember rightly. The old diode that lives next to the battery is no longer connected to anything. 12v battery obviously, bulbs, switch gear is fine, left the 6v horn as it is used so rarely and is now insanely loud and annoying.

Can't remember too many specifics as it was done a while ago and sort of bodged together over a period of months, some of which was spent running at 9v using the new stator with 6v gear. Lights were fantastic for a couple of months at least.
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'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

[Pjay]

[MCN]

[Teflon-Mike]

[Pjay]

[Teflon-Mike]

[Pjay]

You're just shit at Sat Navs.

Besides, the poor guy just wants to buy readily available bulbs fs.

[MCN]

[Pjay]

[Ste]

I've got OS maps on my phone.

Yes there are times when a big OS Landranger map or such like is useful but for everything else, Google Maps navigation is excellent.

Of course, if you've got a potato GPS on a potato phone then your experience will be bad.

[RhynoCZ]

[MCN]