1981 6v cg125 ridiculously high voltage output

[tom050162]

So I've recently got round to sorting the electrics out on my 1981 cg125 and come across a whole bag of issues. To begin with, the voltage from the generator is reading around 6-8v at idle. With increased revs the multimeter has been showing up to 38v!!!

Really surprised, currently running 12v bulbs and they're still being blown as clearly they can't cope with the over voltage they are dealing with. Not sure what wire to use from the Genny, as Im aware they run a direct ac lighting system so are regulated by the battery. The battery is currently showing 3.8v across the poles so not great and doubt it's charging!

Any chance some of you guys have any ideas? I know the rectifier regulates battery voltage, any way of testing the silicon diode? But doesn't explain the massive voltage variance from the generator.

Lastly does anyone have a schematic for the b/c model from 1981 I could pinch to check the earths and wire feeds?


Thanks in advance,

Tom.

 

[irk miller]

https://www.youtube.com/watch?v=F8EjV0IjW9Q

You can test diodes. Definitely sounds like it's not regulating power. I have no idea what voltage your stator is supposed to produce.

 

[tom050162]

As far as i'm aware it should be producing around 7-8v max so it doesn't blow the bulbs etc. Although the rectifier is only a 2 pin used to convert the AC from the genny into DC to charge the battery. So as far as i'm aware it does not regulate/rectify the feed to the headlight & running light system.

 

[irk miller]

As far as i'm aware it should be producing around 7-8v max so it doesn't blow the bulbs etc. Although the rectifier is only a 2 pin used to convert the AC from the genny into DC to charge the battery. So as far as i'm aware it does not regulate/rectify the feed to the headlight & running light system.

Here's the wiring diagram. The lights appear to be regulated power.

http://www.robocog.dyndns.org/cg125/wiring/cg_BR_S&T_wiring.jpg

 

[tom050162]

I'm afraid that wiring diagrams from one of the newer bikes, mines a 6v points system with direct ac from the generator. Doesn't run a CDI so that loom isn't the right one, I've found its supposed to have a ballast resistor in the circuit which I've wired in but it appears to be smoking which says to me there's too much current getting to it?

TOM.

 

[irk miller]

They're all 6v, and all the diagrams are on that site
http://www.robocog.dyndns.org/cg125/wiring/

Sent from my iPhone using DO THE TON

 

[Sonreir]

I don't see any unregulated or unrectified versions of the CG125.

I don't think your headlight should be running from AC and your battery not charging seems to be a pretty good indication of your charging system being hooked up incorrectly.

From your alternator (yes, it's an alternator and not a generator), you should have a yellow and a white wire, both going directly to the regulator/rectifier. The output of the R/R (on the red wire) then goes directly to the battery's positive terminal.

 

[tom050162]

I've sorted it now anyway.

And the voltage isn't regulated for the lighting system it simply has a ballast resistor connected the the +ve side of the loom reducing the voltage when the revs pick up. The resistor was incorrectly installed and therefore would not prevent the voltage from spiking, there is a rectifier in the loom however this is onlf used for the battery's charging system to convert the AC from the alternator into DC otherwise yes. My bike is wired to receive AC power direct from the alternator, the loom was factory from a japanese 1981 cg125.

The rectifier in the loom is only a 2 pin silicon diode so the bike has no regulator only the ballast resistor Sonreir

I don't see any unregulated or unrectified versions of the CG125.

I don't think your headlight should be running from AC and your battery not charging seems to be a pretty good indication of your charging system being hooked up incorrectly.

From your alternator (yes, it's an alternator and not a generator), you should have a yellow and a white wire, both going directly to the regulator/rectifier. The output of the R/R (on the red wire) then goes directly to the battery's positive terminal.