Not charging

I have a 1981 Xj750r Seca. And the system is not charging. Bike shop told me that I need the stator and regulator changed. I tested the regulator and the diodes test out fine. Not when i tested the stator at the 3 white wire on the plug it tested out at 1.2 ohms each. Now in my understanding that is bad? Any input would be great here. Battery is also brand new.

 

in this link you will find tests and specs for charging system
Checking Alternator Stators:

Measure the resistance across each pair (white1 to white2, white1 to white3, and white2 to white3) of the three white wires (white1, white2, and white3) at the connector; the specifications should be:

0.50 ohms +/- 10% for all XJ550 models.

0.46 ohms +/- 10% for all XJ650, all XJ700, all XJ750, and XJ900RK models.

 

Checking Alternator Rotors:

Measure the resistance across the two lead wires (usually brown and green) at the connector; the specifications should be:.

4.5 ohms +/- 10% for all XJ550 models.

4.0 ohms +/- 10% for all XJ650, all XJ700, all XJ750, XJ900RK, and XJ1100 models.

3.5 ohms +/- 10% for all XS1100 models (field coil).


Note that worn, dirty, or damaged alternator brushes can affect these readings, as can "dirty" copper commutator rings on the rotor face (where the brushes contact the rotor):

 

I had measured the resistance on the stator, it came out to be 1.2 ohms across every wire. I was curious to know if that’s considered a faulty stator?

 

yes that would be way out of spec .did you disconnect connector when you did the test?
touch both your probes together and see what you get for a reading of ohms on the probes, cold be the meter odd that they are all the same.

have you ohmed out the rotor it could be that your brushes are worn and the rotor rings are dirty you will have to open it up any way so check that too.
you can clean the copper rings with a hard eraser then ohm them out

 

even new batterys can be bad .
is it hooked up correctly there were are 2 styles of batterys for your bike plus on right side and plus on left side

so when you start bike and put meter on it you get no rise in voltage to 14.6 volts at 2000 rpm?

 

The battery checks out at just under 13 volts off the bike. Plus on the righ and negative on the left. And I did that test on the stator at the connector. Meter checks out. I ohmed the ring on the inside of the cover and it came out at 5 ohms from the inner ring to the outer ring. Is this correct? I did measure the brushes and they came in at 3/8” so they are way low. I think they are supposed to be 17mm not 10mm. But would that cause the stator to read bad ohms? It tests the 1.1-1.2ohms off the bike and by itself.

 

The brushes I measured from the base they are mounted in to the top of the brushes. That’s how
I got the 9.5mm

 

. NOTE: Alternator brushes should be replaced whenever they are less than 11mm in overall length......the factory maintenance interval indicates that you should expect to replace these brushes every 8-10,000 miles. Factory brushes have "wear marks" (scribed lines) on the brush to indicate their wear limit; these aftermarket brushes also have the scribed wear line. Overall length of these brushes are 17.10mm, with 9mm of length from the wear bars to the contact end of the brushes:

 

so you have 3 issues
out of spec stator out of spec rotor and brushes that are to short.

replace the brushes (cheapest part) then go from there

www.xj4ever.com sells all 3 parts

• Charging System

 

So I went out and double checked all my readings.

Stator at white wires-1.1, 1.2, 1.1 consistently. That clarifies is as bad?

The brushes i measured from the scribe mark to the top of them at just under 3/8”. So just under 10mm. Also bad?

And the rotor I believe is the big copper wheel inside the stator case attached to the crank? It has two clear circle marks. And my reading from the inside small ring to the outside larger ring is 4.9. So that is bad also?

Hope all this info is clear enough. Sorry first time doing electronic diagnostics.

Reasons for all this is I have no voltage change at the battery throughout the rpm range. It will just run for battery power. And my headlight does not come on at any rpm either

 

did you touch the meter leads together, get a reading and subtract that number from the reading on the wires?

 

What about checking AC Voltage on the white wires during engine running at idle and 3000 rpms?

 

Not sure if it applies to your bike, but I had a similar problem with my 81 XJ650. Replacing the rectifier/regulator solved the issue.

 

all 3 are out of spec
stator and rotor are both out of spec by more than 10% that makes them bad unless your meter just can not measure well at that range.
brushes are shorter than 11mm bad out of spec.
3 strikes as i see it .
I would click on the charging system link provided above and look at the prices see if you want a rebuilt stator and rotor.

you could just buy the brush set up from www.xj4ever and see if your problem is solved you are going to need a new set any ways.

then it is up to you to get new(rebuilt) or used stator and rotor or a used setup.

can you borrow a different meter and re test the ohms?