Topic: CB125s electrical problems

[mazingerzeca]

Hello all.
I discovered the problem when I saw that if the blinkers were working, the rear light and headlight faded out. I meausred the voltage in the battery and it was about 5.5v.
I disconnected all the devices from the battery and the voltage raised to 6.1v. So, I started connecting everything again, to check which was what was lowering the voltage. The fact is that the voltage fell to 5.5 when I connected the ignition coil. In fact, there was a spark (if the key was switched to on) when I connected the coil to the positive pole. I checked for continuity between the negative pole and the positive pole and it appeared when the coil was connected to positive. I don't know if it is normal and I should look for the problem elsewhere, or if the coil is on short-circuit, or the condenser, or both. How could I test it with a multimeter? The bike, except from the fact that the current is too low for mantaining the lighting and blinkers, runs normal. Any ideas?

[kghost]

You check the resistance of the coil.

Sort of sounds like a crap battery.

Full charge should be 6.5 - 6.6 volts........if its weak the electrical load will pull it right down.

What's the voltage at the battery when it's running w some rpms?

[mazingerzeca]

The battery is new. A crappy battery was my first thought.
I checked the condenser for continuity, and it has continuity on both directions, so maybe this shouldn't have?

[kghost]

Condenser will make your points arc and the bike run like junk.....but it doesn't account for your voltage drop

[grcamna2]

You check the resistance of the coil.

Sort of sounds like a crap battery.

Full charge should be 6.5 - 6.6 volts........if its weak the electrical load will pull it right down.

What's the voltage at the battery when it's running w some rpms?

Right, put a digital multimeter on it after you have the bike warmed up & idling & then proceed to vary the rpm's & check out the voltage as it spikes at the desired(shop manual specs)engine rpm's.Then proceed to turn the lights & horn on & off at different rpm's while observing your multimeter.The factory Honda manual will have the acceptable specs for the correct voltage drop.
The engine may have a weak Stator(A.C. Alternator) or rectifier which will cause it to have low voltage..,test that by the book also.Clean all the Ground strap points on the wiring harness & especially the rectifier mounting where it touches the the frame: must have a shiny metal frame connection(no paint to interfere w/ the rectifier frame ground connection.

[grcamna2]

Is she fully charging yet mazinggerzeka ?

[mazingerzeca]

It's being very difficult to solve the problem. I've tried everything. I've cleaned all the connections. The battery is new. All the bulbs are the correct voltage and watts. The battery is charging well according with the manuals, but I still have the same problem. With the battery fully charged, everytime I use the blinkers the headlight and the rear light fade a little.
The problem is that I have to pass the periodic inspection (I don't know the name in USA, the MOT in UK), which I failed due to this problem. I have hidden under the seat a homebrew battery with four 1,5v batteries connected and the blinkers connected to it, just to pass the inspection, and after it, I will install a full 12v system on the bike.
I've done a search and have discovered that this problem is very common with this bike, and probably the definitive solution will be the 12v upgrade. I've read that a 350 alternator will fit, using the rectifier and regulator from this bike also. Other people rewinds the 125 alternator. I still don't know which route will I follow, but I will let you know how it works.

[grcamna2]

Yes Sir, I've experienced that same problem on the CB100/125S's that I've owned over the years..,there is always a low power situation when using the blinkers w/ full lights/brakes on,especially at idle... A 12vt. system upgrade sounds like an Excellent idea 

[grcamna2]

I'm interested in a future upgrade to the 12 vt. system from the stock 6 vt. on a CB125S and wondered if you know of a good place to look on the computer that will document the entire procedure along with a list of necessary parts that'll finish the job up ?

Have you done this job to your CB125S yet mazingerzeca ??

[fendersrule]

The 6v system sucks. Its also highly susceptive to braking bulbs if not maintained correctly.

My cb125s gives very "dull" blinker and tail brake light with a new battery. The turn lamps stay on and don't blink, and you have to look close enough to see the lights are actually on.

I'm buying a new flasher unit as a start.

Some of it may be that my low on my headlamp is burnt out, so I have to keep the high on. Do you guys know of a cheap replacement headlamp?

[grcamna2]

I'm interested in a future upgrade to the 12 vt. system from the stock 6 vt. on a CB125S and wondered if you know of a good place to look on the computer that will document the entire procedure along with a list of necessary parts that'll finish the job up ?

Have you done this job to your CB125S yet mazingerzeca ??

How's it going mazingerzeca ??

[mazingerzeca]

Hello.
Sorry for being so late to response. I had the "notify" option on this thread, but I didn't receive any message notifying for responses.
Anyway, I passed the MOT with four 1.5 batteries hidden under the seat and connected to the blinkers, so the rest of the lights didn't fade off when the blinkers were lighting. Here, in Spain, you have to have the lights on when you use the blinkers in the MOT. But this is the last summer that I'm using the 6 volts battery. I'm planning to convert to 12v this winter.
I've read about this conversion, and some people installs a 350 stator, which fits on the 125s, but I've read that this doesn't charge the battery enough. Probably I will rewind the stator, according to the method described on the pdf attached.

[grcamna2]

Hello.
Sorry for being so late to response. I had the "notify" option on this thread, but I didn't receive any message notifying for responses.
Anyway, I passed the MOT with four 1.5 batteries hidden under the seat and connected to the blinkers, so the rest of the lights didn't fade off when the blinkers were lighting. Here, in Spain, you have to have the lights on when you use the blinkers in the MOT. But this is the last summer that I'm using the 6 volts battery. I'm planning to convert to 12v this winter.
I've read about this conversion, and some people installs a 350 stator, which fits on the 125s, but I've read that this doesn't charge the battery enough. Probably I will rewind the stator, according to the method described on the pdf attached.

Thanks for that  I'll be doing that 12 volt upgrade when I sort out a few other things in my life;it's Definitely on the "back burner"(simmering on the stove till later  ) for a good time to enjoy the project the most !

[mazingerzeca]

The guy who rewinded the stator tested it, and these are the results.

[grcamna2]

The guy who rewinded the stator tested it, and these are the results.

mazingerzeka,
       I looked at the tests on that link & I hope they do a Mark II alternator w/ a correspondingly correct Reg./rect. assembly that will keep the battery(depending on the capacity of it...)from over-charging.
I like those alternator jobs & tests they are performing !    & hope they decide to do some more. I wonder what size 12 vt. battery they used & where they placed it on the CB125S motorcycle...?

[surveywaters]

Blinkers will cause the lights to dim. Also, if the ignition switch is on and the points are closed the coil will draw power; this is how you end up with coil guts (wax) all over your cylinder head. All this is normal for the old 6v system and DC coils.

[grcamna2]

I really like the little CB125S & I'm looking to get an 81' or 82' because those years come standard w/ CDI electronic ignition.

[mazingerzeca]

I think that they used the same place for the battery that the 6v uses. They found a battery Extreme, model XTAX4L-BS gel-cell and fitted it vertically, because there is no acid.

[grcamna2]

That sounds like an excellent battery choice & placement.
Please let me know if they ever do a Mark II test !

[mazingerzeca]

Well, finally I've done the 12v conversion.  This is what I've done:
First, I tried to do the conversion with the CB350 rotor. So, I installed the CB350 rotor with a 12v battery (YTX4L-BS) and a regulator/rectifier from a Yamaha XS400. It worked... more or less. The CB350 rotor uses the same arrangement that the CB125s uses. With the lights off, it uses 2 of the six coils of the stator, and with the lights on, it uses the six coils. The power generated by the Alternator was very small, a little more than 12v, not enough to charge a battery. After reading a lot about the CB350 stator, I found out that the CB350 had a lot of charging problems, but someone made an upgrade: http://ricksmotorsportelectrics.com/part/99-101/NzFIb25DQjM1MFR3aW4=
So, I bought a charging kit for a CB350 and installed the Rick's kit. It works perfectly, giving 13,5v at throtle. The only problem is that the resistance needed for the coil, in order to avoid premature wear of the points, gets too hot, so I think I will have to install it under the headlight to avoid the warming as much as possible.

[grcamna2]

If I understand you correctly,did you install an aftermarket resistor on the stock original coil for the CB125S ?

[mazingerzeca]

Yes, I did. I must confess that I don't have any idea of electricity. In the pdf regarding the conversion that I attached, it was explained that with a 12v system the points would wear very fastly, given that the amount of current that the coil was receiving was twice the current received with a 6v system, which would give a more consistent spark but also would wear the points. The next step should be switching to an electronic ignition, which is very expensive.

[tbpmusic]

...With the lights off, it uses 2 of the six coils of the stator, and with the lights on, it uses the six coils. The power generated by the Alternator was very small, a little more than 12v, not enough to charge a battery. .......

If a circuit kicks on when you switch the lights on, then there is a wire running to that switch which can be re-routed.
I don't have the wiring diagram for your bike, but on others (like 175/350/450), a common quick mod is to permanently activate that circuit. The wire colors are yellow and yellow/white on those bikes, maybe yours too??
Find the wire going to the switch, where it comes out of the main harness - connect it to the other wire that goes back to the stator. On the mentioned bikes the connectors are all set up for it.
This reconnect became stock once they went to lights on all the time rules - they didn't change the harness.
Now you're charging on all stator coils all the time, and eliminated some potentially power-sucking wiring/switch.

[mazingerzeca]

This bike has the same arrangement for the switching between 2 or 6 coils has. As you mentioned, the white wire is connected with the yellow wire when the lights are switched on, and disconnected when the lights are switched off. So, I tried that, I connected permanently the 6 coils, avoiding the power-sucking wire or switch that you mention. But it didn't work very well. I think that maybe this bike was not designed for running with the lights always on (which is compulsory here, in Spain), and the battery doesn't charge enough. A friend of mine, who is an electrician, told me that is not the same connnecting the 6 coils to make them work as if the lights were on, or connecting them on a continuous winding, which is what should be made to produce a more powerful charge.
As I said, I am totally dumb in electrics, so I couldn't solve the problem, which I think is very common on this bike, so I opted for the CB350 12v upgraded charging kit.

[grcamna2]

This bike has the same arrangement for the switching between 2 or 6 coils has. As you mentioned, the white wire is connected with the yellow wire when the lights are switched on, and disconnected when the lights are switched off. So, I tried that, I connected permanently the 6 coils, avoiding the power-sucking wire or switch that you mention. But it didn't work very well. I think that maybe this bike was not designed for running with the lights always on (which is compulsory here, in Spain), and the battery doesn't charge enough. A friend of mine, who is an electrician, told me that is not the same connnecting the 6 coils to make them work as if the lights were on, or connecting them on a continuous winding, which is what should be made to produce a more powerful charge.
As I said, I am totally dumb in electrics, so I couldn't solve the problem, which I think is very common on this bike, so I opted for the CB350 12v upgraded charging kit.

How is that "Rick's" upgraded system working for you ? If it works well for you,I may do that set-up when I switch to 12vt. on my CB125S.
I'm curious if the power from that Rick's upgraded CB350 reg./rect. system tends to slightly overcharge the battery compared to the stock CB350 system ??

I have a 1972 CB350K4 twin also w/ spare parts.I think the stock system for my CB350 twin w/ it's 12vt./12 amp/hr. battery is very sufficient along w/ the 35/35 wt. halogen headlight upgrade as long as my stock system is kept in excellent working order.
I have it all hooked up as per the stock Honda Original connections.