LED brake light wiring help 1982 CG125

[Thomasktown]

Hi folks,
Forgive me if this is in the wrong section.

Any help here would be hugely appreciated, I have tried to research but I can't find a straight answer on wiring (or I'm being a little dense).
I recently bought a LED rear brake light off eBay (from China) this brake light has three wires, red black and blue (photo's attached). I'm trying to fit this light to my 1982 Honda cg125, the old brake light connected via brown grey and green (photo's attached).

I have tried a few combinations (trying to figure it out from the Haynes and Google advise) and cannot get the new led light to work. It works with a 9v, with red as + and the black is -. I'm thinking I may have to splice wires together, but I have no idea which combo to use.

Does anybody have any idea or advise for me to make this work? It would be hugely appreciated!! Photo links for reference of actual lights and wires.

Thanks!!


[img]https://preview.ibb.co/mHgXaL/unnamed-2.jpg[/img]
[img]https://preview.ibb.co/fTwb20/20181114-185256.jpg
https://preview.ibb.co/hN7S9f/unnamed-1.jpg
https://preview.ibb.co/mHgXaL/unnamed-2.jpg[/img]
[img]https://preview.ibb.co/fTwb20/20181114-185256.jpg[/img]

[weasley]

Isn't the CG a 6v system from back then? Is the LED light for use with 12v?
____________________
Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[Teflon-Mike]

OTMH a 1982 CG aught to be a) 6v and b) AC-Direct-Lighting.
So IF original... and after thiry odd years that's a very big 'if'

First off, the engine needs to be running for the head-lamp and brake lamp to work... they should get un-rectified, IE still alternating current, and unregulated, so volts going up and down from + 6v nominal to -6v nominal, with lpeaks possibly around the 16v mark....

LED 'lamps'.... Light-Emmiting-Diode... diodes being one-way-valves for electrick... that emit light.... they will only pass current, and they will only give out light when its flowing one way.... and if rated at nominal 12v, they will have resistyors in series to draw the current they depend on to chuck out light.. so they will only get enough volts to make them make light, whgen the wave is over 12v... and when the wave goes peak... they will likely 'blow'.

But... of course, you should know all of this, if you know enough to be modding ancient Mag electrical systems... If not THERE is your problem....

There are two solutions:

a) put it back to standard, use bits listed in the brochure, arranged as the manual, should work like the manual says... with TUNGSTEN bulbs... and 6v ones.

b) rewire the whole bike to 'modern' 12v battery stabilised, fully-rectified & regulated convention...

You will need to change EVERY bulb on the bike, including the speedo back-light and idiot tell-tales; you will need to change the horn, and the flasher unit, as well as swap or modify the switches on the handlebars, which are wired to 'not' actually switch the supply to the lamps on and 'off' but redirect AC current through the head and stop lamps when 'on'. Oh.. and the magneto will need swapping out too, and probably the ignition system.....

It CAN be done... and the simplest way is probably to pillage the entire loom and electrical equipment, switches, and generator from a 12v DC Chinese CG clone or derivative.....

BUT, its no small or cheap job..... likely to reveal a whole can of spagetti in Previous-owner bodged and mods, and could fix them too along the way... but still a pretty whole-scale 'project' JUST to be able to use cheap and nasty Chinky after-market tail-lamp, me-thinks.

BUT there is the problem... you have a very old bike, with an even older design of electrical system, making Alternating-Current at nominal 6v... supplying stop lamp only when engine is running... and you are trying to fit a modern LED lamp designed for a 12v DC system with permanent battery live supply........

Go figure.
____________________
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?'

[-]

Another beardy hipster monstrosity CG125?
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[Thomasktown]

[Thomasktown]

[Thomasktown]

[bikenut]

wemoto stop and tail ??

post a wiring diagram to clarify some stuff, there may be a "work around", which may or may not be worth the hassle.
____________________
nuts about bikes

[-]

[Teflon-Mike]

The old CG's tail-lamp, OTMH, was a rather overly big metal shelf bracket thing, with a plastic lens on the back, with a window in it to let a bit of light out and illuminate the number-plate.

When you say that it's 'smashed'.. do you mean the lens has chattered, or do you mean the whole thing, lens, and the metal bracket has turned to rust in your hand?

IF just the lens, this is common damage, and the lenses themselves are actually not all that expensive... maybe a tenner.

After-market LED lamp, apart from not being what you expect, or actually working.... quite often use red-coloured compoment LED's... cos stop and tail lamps should be red.... BUT they have no ilumination for the number-plate...... and that would be a pull and points offence as well as MOT fail...

LED 'bulbs' in an ordinary tail lamp can suffer the same, cheaper ones are often RED component array, and dont shine white light on the number-plate through the window...

There's also a phenomina with LED's in that whilst they might look very bright.... at short range.... actually they aren't all that bright at traveling distances... A-N-D they are peculiarly directional.

The brightness 'thing' is to do with a thing called the inverse square law; basically light travels in a straight line; you double the distance from the source, the 'area' that light has to iluminate is quadroupled, double the distance, 'squared' cos the viewing plane is a square; hence you only get 1/4 the brightness at 'range'

NOW, a 15Watt tungsten light-bulb chucks out 15w of light in one big chunk... to get the same amount of light out of an LED 'array', the lamp will probably have something like 30 individual component LED's... each chucking out a tiny fraction of the light.... cumulatively, they 'look' as bright, when you are at the sort of viewing distance to take notice.... move further away, to the sort of distance you would like SMIDSY car drivers to take notice...

....and think on this.... High-Way-Code says the following distance should be at least 2 two-seconds... at 30mph, that is aprox 13 meters per second, so a two second gap is about 25m.... go pace it out, that is NOT very far, but a feck site longer than your arm!!! And that's the shortest distance a following driver should ever be looking at your tail-lamp from.... now walk to the end of the street... maybe 1/4 mile, about 400meters... that is the sort of distance when you want the following driver to 'see' your tail lamp... and apply the inverse square law..... you will only get something like 1/4ooth of the brightness of each light source.... your one 15watt light source is going to be stretched pretty thin over that range..... 30 individual LED's, each chucking out 1/30th the lumins, will be stretched even thinner... to the point odds is they wont even be seen at all.

In practice, LED's don't drop off 'quite' that much; reason being that to get the volume of light to still get 'some' adequete brightness at range, they use more of them... and because LED's are very much more efficient light makers than hot tungsten wire... they can, and still not draw anywhere near as much electric current....

BUT we get to the directionality..... a tungsten wire filiment chucks light pretty much evenly in every direction; which is why traditional lamps have carefully placed reflectors and lenses, to catch light going in less useful directions and chuck it in more useful ones. LED's, chuck MOST of thier light in a straight line like a lazer.... hence so many of these after-market LED lamps dont even bother with a reflector or lens; the light is pointed straight back anyway.... BUT it is ONLY pointing straight back.....

We got some LED array 'bulbs' to fit in a conventional lamp socket; on my bike, it has two bulb holders, both bulbs angles down and out a bit from the middle.... wonderful.... it sent brilliant red light at the kerb on either side of the bike..... not a LOT went through the lens for any-one following to look at; on the 125's... only had one bulb in the lamp; and it pounts almost straight back.... turn the lamp 'on' and you actually get a circle of red light on the lens... and dark corners, there is almost no diffusion happening, the light travels in a straight line.... Brilliant so that the car behind you, that already knows you are there an see... absolutely CRAP for any-one pulling out of a side turn or coming round a corner, who DOESN'T get that straight on line of sight, to whom the lamp may as well be 'off'.

So, the effect of LED's is often a con, they look really really impressive and 'bright' to the owner/rider that fit them, who will usually be no more than arms length from the lamp, and within a pretty mild angle of straight on from it, to see, and think "Gawd, that bright".... In practical use; other traffic WONT see such brilliant 'bright' light from them, because they are not that close, and the distance drop off sees them dim very rapidly as you go away from source... only folk that WILL see bright light, and enough to be dazzled and anoyed by them are immediately following drivers, directly behind who, really are the last people on the list you need or want to see them so well.....

Oh... and brake lamp.... typically something like 21w over 15.. the brake light will be notionally about 1/3 brighter than the ordinary tail lamp..... you fit LED's... that following driver gets the full brightness.... and when you brake.... a) the brightness doesn't get 'so' much brighter that they are made to take notice... and b) they are probably already annoyed by the brightness and NOT paying attention to it.... especially as most car drovers dont obey the 2second rule and will be following too close anyway.... A-N-D... since LED lamp has this large distance dimming phenomena, they will likely be drawn ion closer still, as if they back off, the lamp seems to get a lot dimmer, and thier depth perception is screwed.....

So, all-told, I am NOT a huge fan of LED's and the supposed wonderful benefits of the 'extra brightness'.... that';s not real indicator of how-usefully that light gets out, or what notice any other traffic will take of it, and its that taking notice that's really the important bit.

LED lamps can be great, BUT... they have to be designed to get that usefulness as much as get any brigtness from them... universal jobbies tend to be a one size fits all abortion that dont have much design consideration, beyond how to make them as cheap as possible... which compromises the usefulness even further.

LED's 'can' draw a chuck site less electric than tungsten equivilents; we whole-sale used them on Snowies 125, because of the marginality of the generator compared to the electric crap she wanted it to run... and as an idea, just swapping out the tungsten idiot lamps in the dash-console for LED's 'saved' about as many watts of electric as the headlamp used! About 20 if memory serves. Doing the same with tail and indies and side light, freed enough electric for her to run a 55w headlamp bulb instread of a 35w one, electric heated grips, a sat-0nav and a phone charger...... BUT... took a heck of a lot of care and forthougt to get that benefit.

Fitting 'Cheap' LED indies, will usually make more problems than it solves, and because the flasher unit is load dependent, and will flash mega-fast with a lower wattage bulb or LED fitted... comon way to get the flash rate to slow to MOT limits, is to add a 'balast' restistor... which puts the exact same electrical load, and hence wattage draw on the flasher as the tungsten bulb did... so no extra amps to be found them! Add that the light is now more directional, and you WANT folk not looking direct at the lamp to 'see the light' and not knock you off.... cons are starting to stack up, and pro's not getting a look in... about the only things that you might practically gain from using LED indies is, that they are Cheap... and to some.... may 'look' more stylish.

Back to your dilemah....

IF it just be a smashed lens.... buy a new one, and fit a conventional tungsten bulb... in fact, its an old-onda, get on the Dave Silvers web site, order a couple of lenses, and a few bulbs... remember they are 6volt.......

Lenses are notoriously prone to getting cracked or smashed, from backing the thing into an overflow pipe sticking out the wall when you roll bike onto the center stand (Ooooh! That bludy over-flow pipe! Whole chuffing wall, it HAS to be in that 4" where tail lamp is going to hit it... I SWEAR it moves too... sits there and lines itself up where I park the bike, like a gaolie predicting where the vall gonna come from a penalty shoot-out!!!!) To some-one running a shopping trolley in to it in a car-park, to you kicking the thing off when you swing your leg over the saddle...... Have a spare... cos its an almost garanteed pull-point for plod.....

Bulbs? 6v bulbs are rare thee days; they are not the sort of thing you can just pick up in Halfords or your local motorfactors or at the petrol station.... A-B-D old 6v systems, as alluded to, AC direct, are not the best stabilised, so bulbs have a habbit of 'popping'..... and modern bulbs, made down to a price/quality, often rely on the stable supply to give them any reasonable 'life'..... so carry spares.

Whey back when, it was just the norm to carry a couple of spare tail lamp bulbs under the seat, for this very reason, and that's when bulbs were better and easier to come by.

Spend some time, cleaning the bulb holder, cleaning the wires and the contacts and bullet connectors. Use a 'little' frease NOT silicone sealant, around the lamp lens to help keepo water out, and you 'may' spray a LITTLE WD40 in the lamp to repell moisture... that's what WD40 is for, W-water D-dispersant, formula 40, THAT is what it was develoiped for, NOT oiling motorbike chains or unsiezing rusty nuts and bolts! It is not a release agent like plus-gas... its a water-dispersant.... and should be good to go and as likely as reliable as can be.... BUT even 12v tail lamps on little bikes, can be a bit flakey, and blow with annoying regularity, dont expect it to last like the bathroom light bulb!

Oh... and take care when parking and mounting.... that tail-lamp is still vulnerable..... a-n-d by the inverse law of sodd... IF you have spare lens... odds is you will never need it.... if you dont.... murphey will rub hands with glee and move that over-flow pipe to smash the one you got! Lol.
____________________
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?'

[stinkwheel]

Your tail ight is NOT AC. Brown wire on a small honda is DC. Same one that powers the pilot lights and clock back lights.

A 6V LED stop and tail should work. However, the DC output is not very "clean" and could upset some LEDs. For this reason, I'd suggest fitting one designed for a 6V positive earth vehicle which has some added electronics to reduce its polarity sensitivity.

The green wire is earth, the brown wire is the tail light feed. The yellow on green is the brake light feed.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Elektroniker]

[stinkwheel]