cg125 not charging battery

[skikman]

1999 honda cg125 not charging.put multimeter on battery wires and only getting 10-11 volts.even reved up 11.7ish volts.changed over rectifier with one i found in a box of spares i have in the garage so not 100% sure its ok but it fitted.still the same.no charge.so could it be stator?is there a way of testing stator?anything else i should look out for?

[Taught2BCauti...]

Check the wires coming from the stator - there's usually 3 yellow ones - and trace them up to the connector at the reg/rec to make sure there's no damage.

Unplug the connector and call the wires 'A', 'B' and 'C', then using a multimeter set to a low ohms range, test the resistance between A and B, A and C, and B and C - then post back with the results.

You could also try removing the inspection plug from the stator casing and have a sniff for burnt wiring - it smells pretty awful!
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Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[skikman]

i took off flywheel and stator looks fine.no burnt marks or discolour.there are 6 wires coming from the stator.green,yellow,white,green/red,blue/yellow going to square connector and a single black/red going to a bullet connector.how the hell do i test this?

[Nemo]

Looks like you want the one actually attached to the stator, can't see properly but looks like green, yellow and white.

Do as above, and also make sure there is no continuity from those wires to ground.

If you get a numer 1. it means there is no continuity.

Also, set to AC volts and when the bike is back together check output of each of the wires from the stator.
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[Taught2BCauti...]

Looks like you have split windings - the coil at the 12 o'clock position is for the ignition circuit, the two wires at the 2 o'clock position are for the ignition pickup, so the other 6 coils are for the charging circuit.

One end of the six coils will go to earth (green wire), the other end will go the reg/rec (white wire), and the yellow wire is the centre tap - which also goes to the reg/rec.

Measure the resistance between:
1. Yellow and Green =
2. Yellow and White =
3. White and Green =

The first two values should add up to the third value.

The engine won't run with the wires unplugged, so after testing and re-buildng, set your meter to AC Volts and check the output between Yellow and Green, and White and Green.

There should be a red wire going from the reg/rec to the battery, so check this with the meter on DC Volts (red meter lead to red wire, black meter lead to battery negative), where it comes out of the reg/rec and where it connects to the battery + terminal - the readings should be the same at each end.

If not, see if you can trace it's path to the battery + terminal - there's probably an in-line fuse somewhere.
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[WD Forte]

The diagram I found shows the CG doesnt have the usual star wound 'floating' 3 phase stator like many bikes but a 2 phase type
with one end of the windings connected to ground and centre tapped by the yellow wire
Both yellow and white go to the RR but the yellow is tapped off to
supply the lights

I'd guess they both have pretty low resistance to ground but
tested open circuit I reckon the white should have a bit more then the yellow.
how much I dont know it may be a case of rtfm

https://binatani.com/wp-content/uploads/2010/09/honda-cg125-wiring-diagram-single-cylinder-engine.jpg
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bikers smell of wee

[skikman]

[Taught2BCauti...]

I'm not sure exactly what readings you should be getting - but at least they are not short-circuit or open-circuit, so I would say you are good to put it back together and test it further.

When the connector is plugged back in and the engine is running, measure the DC volts between earth and the red wire coming from the reg/rec, and again across the battery.
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[WD Forte]

They sound about right, you're not going to see much resistance
in those coils.
Tip:
When reading very low resistances short the meter probes
together first and note the lead resistance.
It can often be say 0.5 ohms-ish so you subtract this from the reading taken on the coils to get actual values.
____________________
bikers smell of wee

[skikman]

right.bit off trouble getting the flywheel back on.mushroomed the top of the shaft with the puller.anwway back on and bike started with red meter lead to red lead going into reg/rec,black meter lead to engine.9.8-10v.same across battery[not enough]

[Taught2BCauti...]

OK, now with the meter on AC Volts, measure between the White wire and earth, and the Green wire and earth.

Unplug the connector from the reg/rec and measure the same 2 wires again.

This should determine whether it's the stator or the reg/rec causing the problem.
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[skikman]

[skikman]

right.pulged in white to engine 10.6,green no reading.unpluged[bike still running]white to engine 12.8-13,green no reading

[Taught2BCauti...]

Sorry - should have said Yellow wire for the second reading, the Green wire IS earth

I would have expected around 20 - 25VAC from White to earth with the engine running and the reg/red unplugged, so beginning to suspect the stator.
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[skikman]

[Taught2BCauti...]

That's definitely low - can you see a way to test the resistance across the individual coils?
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[skikman]

[Taught2BCauti...]

I can't really tell from the pictures, whether the coils are wired as 2 sets of three, or 3 sets of two, but you would probably need to de-solder the connections to measure the individual resistance.

Best way, would be to compare the resistance readings you took before, with a known good stator, using the same meter.

Since you are only getting 8.2 to 13 volts AC out of it, I would say either the windings are duff, or the magnets in the rotor have lost their power.
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[skikman]