CB125S Charging problem

[yamaico]

Not VMX, but I need some help from the brains trust, and I recall that a few of you have early CB and SL Hondas.

I have a mate that has a '71 model CB125S that he rides around on historic rego. The battery charges fine until the lights are turned on and then it gradually begins to discharge. The battery is new and the rectifier checks out fine, with only about 60mV AC at the battery. When running, the battery voltage is around 6.6V, but when the lights are switched on the battery voltage reads 5.8V and begins to drop from there. The current draw is around 1A running and around 6A with the headlight on high beam, which is about correct for a 35W globe.

I suspect that the stator is the problem, and recorded the following AC voltages from the connected stator wiring:

Wire Colours   Headlight Off       Headlight On   
                     Idle      2000rpm  Idle      2000rpm   
Pink-White      5.6V      5.8V      5.4V      5.4V   
Pink-Yellow     7.8V      8.2V      5.6V      5.7V   
Yellow-White   3.1V     3.1V      200mV   200mV   
               
Any ideas, or any other tests that I could do?

Thanks,

Pete.               
               

[cyclegod]

Sounds like the lighting coil is faulty or there is an open circuit somewhere. I found with my TS185 that if I replaced all the globes with LED equivalents and an electronic flasher unit battery life improved significantly.

[yamaico]

Thanks for the reply C-G. The Honda doesn't have a lighting coil, just an alternator. The LED globes are a good idea though, and will reduce the draw on the system significantly,
Pete.

[bazza]

Non Honda related but will have a beer for you tomorrow night at the "poste" in Mt Eden....lol

[Tim754]

Precisely the same problem on SL100 , eventually replaced alternator set up to check , with another 2nd hand unit . All fixed. Tim754

 Sure the battery is in good order? Cheap 6 volt wet cells can be nasty from new.

I would 1 or 20 spare stators I think

[Daryl Jones]

I'm up the bush and don't have the manual with me, but I'm pretty sure the Headlight runs on AC, direct from the coil (White wire), through the switch.
The pink wire goes to the rectifier and charges the battery. Yellow wire is from the ignition coil.

You're only getting (less than) half, the generated power, via the Battery, hence the discharging.

Cheers, DJ

[yamaico]

Non Honda related but will have a beer for you tomorrow night at the "poste" in Mt Eden....lol

Wish I was there Mike

Precisely the same problem on SL100 , eventually replaced alternator set up to check , with another 2nd hand unit . All fixed. Tim754

 Sure the battery is in good order? Cheap 6 volt wet cells can be nasty from new.

I would 1 or 20 spare stators I think

Thanks Tim, I thought you might know. I've tried another battery and had the same problem. Would there be any chance I could buy a stator from you? No problem if not.
Pete.

I'm up the bush and don't have the manual with me, but I'm pretty sure the Headlight runs on AC, direct from the coil (White wire), through the switch.
The pink wire goes to the rectifier and charges the battery. Yellow wire is from the ignition coil.

You're only getting (less than) half, the generated power, via the Battery, hence the discharging.

Cheers, DJ

Thanks Daryl. I've downloaded a wiring diagram and you are correct, so it all points towards the stator,
Pete.

[SUZUKI311]

Not sure where you live, but if you Send your stator to Bert Neville, at Small Coil Rewinds, Edols St, Nth Geelong, he will repair your original one no dramas. very reasonably priced and excellent workmanship.

[crossedup2]

This help?

http://www.ebay.com.au/itm/honda-cb-xl-100-125-stator-nos-/351296888726?pt=AU_Motorcycle_Parts_Accessories&hash=item51caed1f96

 

[crossedup2]

Must have or someone else was quicker!
 

[Tim754]

Of course I will rip one off a spares engine for you. Not till Monday so time to PM me an address to post it to mate. Hope it gets the little banger going. Cheers.

[OverTheHill]

long time ago but thought all the lights [headlight included] ran off the battery, that's on the common old cb125 single, not sure if the 'S' means something different, so to throw a new twist on it [without reading all comments--as beer time] umm where was i!!, wouldn't be surprised if the lighting switch [if it's one on the throttle [or other side], slide type off dip high--thinking maybe this brings in the extra stator coil [coils] to counteract the headlight draw from battery. Stator i'd think should test with continuity between all wires [don't get confused with neutral switch wire] & nothing to earth [unless faulty of course] hardly ever seen a faulty one--or at least the ones lightly encased in some white stuff. By memory they're un-regulated so would rely on a switch to bring in extra coils. Sorry if this confuses things [look in the off/on/dip switch] & tell me if i'm wrong too. Used to work where we sold then 'new' but of course never gave trouble then did they. There is an early trail bike XL125 i think that ran AC ignition with a seperate coil for that within the stator windings but am assuming yours isn't this type. Back to the beer--that'll sort it.

[Mick D]

All the little earlier Hondas with points type ignitions shared a similar wiring schematic.
That is the ignition, blinkers, horn and brake light circuits were battery linked
whereas the lighting circuit was AC
All three alternator phases were connected to a four plate selenium rectifier, but one off the phase wires was doubled to the handle bar switch blocks as feed for the lighting circuit.
It is accepted that the charging process of dispelling sulfuric acid from the lead paste of the plates does not become effectively active till charging voltage reaches 6.8volts for a 6v battery. A regulated high limit of 7.2 volts is  recommended for safe charging and optimum battery life(for a 6v batt).

Make sure nobody has mistakenly fitted 12v globes in dash or tail.
Classic rego,,,daylight club runs only?
But still a need to comply with the Australian headlight always on rule?
You could get away with a couple of low draw LEDs front and back to avoid scrutiny
A shunt type silicon diode rectifier/regulator will also produce higher forward voltages at lower revs and start the battery charging chemistry sooner than the selenium plate rectifiers will.
But alternator is the remedy path of choice.
Two phases down from once three
One phase to loose then she'll be riding home with the Harleys on the back of the rescue ute

[Mick D]

I honestly don't see myself buying anymore lead acid batteries ever again.

[yamaico]

Bloody hell, how good is this forum. What a great response to a question that's not even VMX related.

Not sure where you live, but if you Send your stator to Bert Neville, at Small Coil Rewinds, Edols St, Nth Geelong, he will repair your original one no dramas. very reasonably priced and excellent workmanship.

Thanks SUZUKI311, looks like I'll be OK, but will definitely put those details in my file.

This help?

http://www.ebay.com.au/itm/honda-cb-xl-100-125-stator-nos-/351296888726?pt=AU_Motorcycle_Parts_Accessories&hash=item51caed1f96

 

Thanks for the lead crossedup2, that would have been ideal, but I have only just got home from work and missed that one.

Of course I will rip one off a spares engine for you. Not till Monday so time to PM me an address to post it to mate. Hope it gets the little banger going. Cheers.

Thanks very much Tim, I'll PM you with the details.

Mick and Overthehill - thanks guys, you have both put some thought into two very succinct replies. It would appear from what you both say that the battery does the regulation. I have checked all the connections and the globe voltage and wattage and all OK. A solid state rectifier will improve things for sure Mick, but as you point out, the stator seems to be on the way out.

Thanks again everyone for taking the time to respond,

Pete.