First post: CG125 6v to 12v conversion

[retrogamer199...]

Hi all,

First post so be gentle. I just got my bike - a first generation CG125 - a couple of weeks ago in a non-road legal state and I wanted to jump in at the deep end and hopefully get it going and looking good for summer. I have come to the conclusion I would like to change the older 6v electrical system to 12v because then I'll be able to use brighter, more modern lights and indicators (the particular ones I want to use are only available in 12v). I know this can be done as I've seen other old 6v CG125's converted to 12v.

I've done as much research as I can, but some things go over my head. I've tried asking others that have done the conversion on other forums and via email but with little response so I'm posting here in the hope of help! I can't really find much online about this topic on a CG125 either.

I've seen 3 ways to do it, from what I can gather . Some people say that all I will need to change is the rectifier to a 12v version (as well as the ignition coil and flasher relay) and some people recommend to modify the stator to output the lighting and ignition coils to one output rather than two, therefore giving more juice in one rail. A third method seems to be changing the stator to a more modern one which requires a bit more modification.

I've already got a new regulator, flasher relay, ignition coil, later CG125 Brazil wiring loom (mainly for the connectors) and I'm replacing all the lighting anyway. I'd also like to use a battery eliminator so no need to charge the battery either.

Now all I need to figure out is, do I need a new 12v stator, modify my existing stator, or just install the new regulator and other bits and be good to go? Either that or I'm completely wrong and about to learn a lot

Can anyone shed any light on this?

Thanks
Nick

[BMWilliams]

Sounds like your on the right track with all the 12v electrical parts and loom. but yea I would change the stator too, so you know you've got one made for powering a 12v system.
Plus the reliability of a new part too, as I can imagine it be the original stator it was built with


Good luck bud
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[Fisty]

Incoming sperg alert.
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[WD Forte]

All quite doable
but will just bung in a factette
Power is power so lets guess the original stator puts out say 60W or 10A at 6V and you fit a 12V RR, you'll get 5A at 12V.
The power output and potential output options depends on various factors like how its wound, strength of magnet etc

I know some old bikes fed AC directly to the headlight
and only rectified to DC for the points/ignition.
Nowadays, there are various methods and options for upgrades and leds in place of bulbs will use the limited power more efficiently.
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bikers smell of wee

[retrogamer199...]

Thanks for the responses. Unless I get alternative advice I think what I will try first is to just change out the reg/rec for a 12v module and see what the indicators and headlight brightness is like before messing with the stator. It might take me a few days but I'll report back with my findings

[Teflon-Mike]

The ignition is an independent circuit; if you keep the 6v stator & points, you wont need to change the coil.

The lighting & charge circuits?

In the 6v arrangement, the lights are on AC direct; unregulated current powers Dip & Main beams, and the stop lamp When 'off' the light switch directs that un-rectified current at the regulator to assist charging for all the other equipment.

AC direct is actually a very 'efficient' system... it has some niggles, BUT, it is efficient, which was why it was used in the olden days. And first fly in your ointment; very easy to go 'Full Rectified DC' lighting; all you have to do is by-pass the AC Direct feed to the light switch, straight to the rectifier, and from memory, on the 6v CG that's just a case of snipping the feed wire to the light switch and tapping it in on a battery fed live... ignoring the voltage for a second, though; this will NOT give you the 'power' for 'better' lights.

Power comes from the generator, and going 'regulated DC', you aren't going to have any more power than you did to start with, and after pumping what you had through the regulator, possibly a tad less.

Yup; taking current for the lights off the battery, you will have all the juice that contains to power lights.... as long as the generator can make more than you take... which if you start fitting higher wattage bulbs, it probably wont.

Lights wont 'dim and bright' with engine revs, as they can on AC direct, especially if the bulb wattage has been increased in nieve belief it'll make lights brighter.

So, think hard on your 'better bulbs'; what power the genny is banging out still has to be shared between everything else switched on, and if the genny ent making enough to supply demand, the battery is a it like an 'over-draft', and it'll only make up the short fall, briefly, IF you 'pay it back'.. If you want to take more watts out on the headlamp, then you have to make savings elsewhere, and on the lower wattages most else draws, and the fact most of it, bar the tail lamp, only draws 'part time', means you will have to save a lot more watts on everything else, than you try giving extra to the head-lamp.

NOW... going 12v starts to become more useful, NOT so you can use common higher wattage 12v headlamp bulbs, but so you can use more readily available 12v devices elsewhere; (you will need to change all the bulbs, the horn, the flasher, and most importantly the battery) and for the most part to find the sort of 'savings' you need, we are talking about LEDing every-buldy thing, from the tail lamp and side-light, and the indies, through its warning lamp and the others for neutral and high-beam.... which begs not just a 12v flasher, but electronic 'Crystal Timed' flasher for LED's.... AND with LED warning lamp, some nifty electrickery to get round the quirk of the stock single bulbs 'reverse earth' wiring, with a 'one way' LED bulb...

Its now getting rather involved..... AND it gets more so..... you want to pick 'better' 12v headlamp bulbs.... well, that suggests the common H4 'car' type bulb fitting. This begs chopping the connector off the wires in the headlamp to fit an H4 plug, for starters, but also a H4 ftting headlamp reflector that the bulb will actually go into....

This, part-mod, would allow the use of an HID headlamp; which conveniently has a mere 35W current draw, not much of anything over 'stock' that could give you a little or breathig space looking for savings elsewhere to power it.. BUT, you have to get a reflector you can make fit i your headlamp bowl, or a complete new headlamp that you can make fit your headlamp bracket, or complete new headlamp AND brackets.. ad the find a new way to mount the indicators, horn, and speedo that share the same 'frame'....

A-N-D... by the time you have chopped all the wiring to get it to stretch or match the new lay-out on the bike, make connectors match, or replaced ones that crumble when you start messing..... you have a mongrel bastard of a wiring loom, that don't look anything like anything in any of the diagrams, with colours changing half way down wires making tracing them a pig, AND so many joints and grafts and pig-matched new and old connectors.... to give grief when you start trying to run the thing every-day.... you might as well have saved yourself a LOT of effort, and hassle, both on the spot ad down the line, getting a few meters or brand new wire, in assorted colours off e-bay; a truck load of Japanese Standard bullet connectors from Vehicle Wiring Products; and the relevent insulator sleeves, shrik-wrap and tape, and a GOOD soldering iron.. and starting from scratch, with a clean sheet of A4 paper and a packet f kiddies felt tips, to draw what you make, 'cos it ENT gona look like the book says it should!

It ent cheap, and it ent easy.. and the niggle over using 6v points generator or making later 12v CDI genny fit your engine, is but SMALL worry in the greater scheme of things.........

But, if you really want to go 12v, probably the surest way about it; and if you can pick up an MOT failed 12v Chiky CG copy 'Spares or Repairs' you probably get all the bits required to do a full conversion, to the book, and a few besides.

Alternatively, and this would be my recommendation; big enough job doing a first time resto; do it to the book and leave it stock.

Lights aren't great, but if properly fettled when you restore and you fit a nice new shiny reflector and clean all the contacts properly to give the stock bulb all the volts it can get, ought to work 'adequately' and probably better than something 'upgraded' badly.
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[retrogamer199...]

Thanks for all the information Teflon but my original question remains unanswered as far as I can make out, on how to actually make the bike to 12v.

I should have been more clear, I'll be using entirely LEDs, which are all 12v, rather than bulbs. I just don't want the lighting to be dim at an unsafe level or non functioning which is my main concern. If I can run LEDs no problem at 6v, then that's great, but as far as I can tell, I can't.

I'll do a good job of the wiring.

I'd really rather not swap the whole engine out as you suggest for another one, might as well just change this one over for the sake of it.

So I guess my question so far has come to, will the original stator on the CG125 be able to provide 12v (or at least enough to power LEDs) or do I have to install a more modern 12v one?

[MCN.]

Teffers you fucking sperg, nothing runs AC lighting.

The scary thing is you pass off your inane ramblings as gospel.

[Teflon-Mike]

I wasn't suggesting you swap out the whole engine; but a Chiky CG copy with 12v electrics could provide the stator, rotor, and cases needed to convert; as well as the CDi and coil to go the whole way 12v, rather than hybridise the electrics so much. Though probably would be less of a faff to swap out the whole lump if it ran; its only seven bolts if memory serves.

Answering your explicit question, will the 6v generator make 12v.... more than likely... whether it'll make more than 12v often enough for long enough to put 12v on a battery is another question..

Generator makes electric in a pulse as maget on rotor passes the coil winding on stator; when the maget passes one end, you get a +ve pulse, the when it passes the other you get a -ve pulse; wave form of voltage is sinusoidal; nominally rated at 6v, that will be 6v 'average' by a 'root-mean-square'... so the volts squared & square rooted to get rid of the + & -, then averaged; the 'peaks' of the sine wave then will be aprox 1.42 x the RMS 'average' voltage.. about 9v ish.. not enough to run a 12v system... EXCEPT that the voltage creases with rotor speed; so they often will make over 13.5v needed to charge a battery... briefly, at the peak of the pulse, and at 'higher' crank revs.. which don't have to be THAT high...

The 6v system will be designed to deliver 6v at not much over tick-over; and its regulated (on the charge circuit) with a simple zener diode; this only provides half wave rectification; it looses the -ve pulses and only lets the +ve pulses pass, while chopping the top off any pulse over, think 6.8v or something like that.. volts can then be 'peaking' at or near 12v as low as 2-3,000 rpm..

Using full wave rectifier regulator; first there's less to regulate; generator wont be making much over the threshold very often, and the more sophistcated electronics, invert the -ve pulses, rather than just block them, while it will 'smooth' the waveform a bit before it starts clipping volts off the top.....

Which does't answer the question, really, but may go some way to explain a 'Yes, No Maybe' one.

And yes I have done this to a 6v AC-Direct Lighting bike, they do exist.. I still own one of them....

Using a four pin, 12v full-wave, regulator-rectifier.. you have two inputs, one output, and an earth. You put the out-put onto the battery +ve; earth to chassis earth/ batt neg. You chop the feed from the AC direct winding on the stator, put that on one input pin; chop feed from the charge circuit winding, put that on t'other input pin... then, when engine running, both generator outputs are feeding the reg-rect, and you'll get whatever volts it's banging out, up to 13.4v, on the battery, to feed whatever you want to run off it.

Now.. whther it'll work, is not the same as whether it'll work 'practicably'.. at lower revs it will be struggling, and any equipment is likely to be taking charge from the battery, while the battery will only be taking charge when the motor is running faster... so we come down to a balance sheet, of how much electrical equipment is taking and for how long, vs how much the genny is giving and for how long...

But it can 'work'.. I did it to a points ignition Yam; genny never charged the battery from dead, but, with a slightly raised tick-over, could keep it adequately charged to run 35w HID and all LED bulbs... provided you didn't expect to run them full time; ie using dip-beam as a day-time running lamp, or doing all your miles in the dark...

Its 'in the margin'.. how much, will be down to how you use it.

Later 12v generators on the e-start bikes, I believe do have a higher out-put rating by about 100w or so, OTOMH, which obviously would be 'useful' and increase the margin; but a stock 12v CG if ridden with the headlamp permanently 'on', not revved hard for very long, very often, and spends a lot of its time sat idling at junctions and the like with the brake lamp and indies 'on'.. doesn't take too tired a battery for folk to start moaning about 'starting problems' or 'charging issues'.

So, back to the question.. Yes, No MAYBE!

You Don't HAVE to do bugger all.. 6v lights can be 'adequete' if properly fettled; FEW motorbikes of any displacement ever have particularly 'wonderful' lights compared to cars, they are all limited by a relatively low out-put generator... Alternator on my car knocks out 130A, about 1.5Kw... that is about 1/6 th total power a CG engine can make! (probably weighs as much as a CG engine too!) So, its a case of copromise; ad the base-line is that a 12v e-start CG's generator is about 'big' as might hope to get, and, even that is no great shakes; mod that with LEDs and HID, yo might get something pretty impressive, for a lightweight, BUT, it'll still it be exactly astounding....

So, what do you hoe to achieve? How important is it? And how much hassle and grief and inconvenience are you prepared to accept, and how much money you prepared to pay for it?

I think it cost me something the order of £150-£200 to 12v the Yam on the 6v points generator, reg-rect was under £15, if I recall; 12v battery I think was £20, LED bulbs totted up though, as did new wire ad propper connectors, new 12v horn, flasher unit etc etc etc. Most expensive piece-part in the job though was an H4 headlamp lens/reflector, which I think cost something like, £35, to get one that ft the headlamp shell; and ironically, THAT, just the nice shiney new silvering and clear bright glass of a well made lens, would have made the 'most' economical, least cost, least effort, least hassle, 'improvement' to the lighting, without any ifs and buts over keeping the battery topped up...

It WAS a good headlamp for a motorbike, with a high quality HID in it, but, an awful lot of hassle and expense to get it, and on a dark night on a wet unlit country road, I would STILL prefer to be in the Honda Civic, which has peculiarly SHIT head-lamps for a car, even when they aren't covered in gunge as they usually are from the tree it lives under!
____________________
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?'

[retrogamer199...]

Mike, Whilst I appreciate the time you've taken to reply, and that is has gone some way to further my understanding of the subject, I find your writing style very hard to follow. One of the chaps I messaged who has actually done the conversion got back to me with step by step instructions, so I'll follow up on this post once I've done it myself.
Thanks
Nick

[Carvel]

Yeah fuck off teffers.
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2002 Aprilia RSV1000R, Cbr600Fs, Mk1 B12, Vfr400 NC30...

Matt B: I can deal with crushed nuts to beat Ollie.

[Fisty]

[CaNsA]

[kramdra]

CG125 will never look nice. Its really not worth the effort If you must do it, abandon the original stator. You cant upgrade it as the points and shit are all in the same place.

Get a decent sized RC brushless motor (from hobbyking) or generator from a proper bike and mount it on the front sprocket cover or swingarm with an idler sprocket, the output from this will feed into any normal 3 phase regulator, preferably one from a proper bike. This will take some minor effort to fabricate..

However a benefit is you could flick a switch to disconnect the regulator and connect an RC ESC/ lipo battery packs and gain another 5kw of power

Its quite interesting what people are doing with ebikes. Many are more powerfull than your cg125

[retrogamer199...]

[WD Forte]

[retrogamer199...]

[Large28]

Hi Nick,

I own a Cg125 1979 and im wanting to upgrade the lighting on it too. I initially thought that this would entail going to 12V, but through this chat ive seen that it might not be necessary! Please could you let me know how its gone with your bike and what you got round to doing. I know enough but not alot, so an idiots guide is preferable!

Many Thanks!

Alex

[unitynotsocri...]

Id just forget about it , drive slowly at night and spend the time you would have wasted getting a 12v Brazil type 2 model which have 12v but follow in the crappy tradition of crappy lighting , after all ,you dont need bright lights as they dont go very fast.


or......swap the whole stator,wiring loom,switchgear etc...etc... everything ..........
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[unitynotsocri...]

p.s. other than being quaint the best thing about the type one was the petrol tank, but even that can be recreated by using an old chinese cg clone tank.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[smallfrowne]

Just to add to this...

I had an '84 CG on points and 6v. Until the stator went up in smoke and I lost the lighting circuit a few miles from home in winter on country roads..

I ended up being given a "project" from the local bike shop as he didn't have any 6v points stators left and we couldn't be bothered rewiring it. The project consisted of a later model stator & flywheel, a shiny Chinese SPORTS CDI + matching coil. Oh, I also needed a CDI genny side cover too, as the old one didn't leave room for the pick-up coil. I did have to tweak the wiring a little, I wish I could find the notes I made now, I've forgotten what I did exactly, but wouldn't be hard to figure out again.

I had full intention of converting it to 12v - I have a rectifier regulator, 12v battery and the bulbs to finish the job, but I haven't bothered. The cdi is AC, so that couldn't care less, and the 6v bulb and battery combo mean it now runs about 8.5v (tested at the battery) with a few revs on, just over 8 at idle. It's been like this for about 700/800 miles now and I've just reminded myself to check the water level in the battery, see if it's boiling off.

But! The headlight is amazing to someone that is used to 6v flickery idle speed light - and it no longer does dip at idle! It looks like a proper bright usable light, and not just a warm yellow glow. The lighting runs off one of the 2 wires you get from the stator (the 2 that normally would go to the R/R), the other wire goes to charge the battery through a diode.

So the headlight and rear lamp is still AC, the brake light off the battery. I don't have any indicators on atm as you can't see them in the daytime anyway. Oh and the instrument bulbs are still 6v, but the clock is visible at night and you can see if you're in neutral without cupping your hand round the thing to the block out sunlight.

Obviously the bulbs might not last very long, nor the battery... but it's summer time now I will be commuting to work & putting this thing through it's paces, without worrying about the lack of a headlight. I'll potentially report back here if/when something goes pop.

tl;dr - Points to CDI conversion running at ~8.5v - nice bright light, potentially bulb poppingly good.