Overheating or stator?

[geluso]

I see the great images explaining the differences between 70-79 and 80-84 stators.

Step 1
Fresh store-bought battery.

Step 2
Does not pass slap test. Does not exhibit any magnetism.

Step 3
Shorted green wire to ground (see photo)
Battery read ~12.8V relatively steady when running
Battery would not go over 13V
Revving to 4,000 RPM

Step 4
12.50 across battery with key on
12.12 from brush screw brown wire to battery negative

12.53 across battery with key on
12.21 from brown wire at plastic junction to battery negative

Step 5
Definitely not getting 14.5 at the battery. 12.8 max revving at 4,000 RPM
Measures 5.6 ohms on stator rings

Step 6
#1 white wire 7.85V
#2 white wire 2.69V
#3 white wire 7.92V

Popped stator off to see if it was blown out before reading Step 7. This little roll bearing fell out. I'm not sure where it came from.

Stator looks very dirty.

 

[Its been a long time]

Please check the stator windings. Each white wire to another of the white wires and to ground. As per -

Regarding a dirty stator, that's normal. Just lightly brush or blow the worst of the dust off. Or just leave it be. Don't use chemicals or solvent.

Please let's see the rectifier/regulator you have, is it the original Yamaha one?

I see from the comments above that you have a questionable Mikes XS ignition coil. If you have a Mikes XS regulator as well, that's quite possibly where your charging problem is. There's lots of problems posted here about them.

 

[geluso]

Thanks for the reply. It is near midnight and dark here. I'll put things back together, test the resistance of the stator windings on those white wires, take photos, and post again in the morning.

 

[gggGary]

This little roll bearing fell out

It should be inserted in the lower case half as shown here.

The rectifier part of the voltage regulator can be tested.
red, black, 3 whites.

 

[geluso]

I read resistance between each pair of white wires. I read 0 ohms, 0hms, and .7 ohms.

Since I read one bad voltage earlier I'm guessing one coil is bad so it messes up two of the three pairs, then the .7 ohm reading is the two good coils making one good pair.

Anyways, those are the reading and that's just my completely uneducated guess.

 

[Jim]

I read resistance between each pair of white wires. I read 0 ohms, 0hms, and .7 ohms.

OL. is an "open"... not zero ohms as you stated. Either way is bad, just wanted to make sure you're clear on what you're reading.
It's the center white that's bad... a broke wire somewhere.

I looked and the only TCI style stator I have has been stripped of it's wires and brush holder. Sorry.

 

[geluso]

Ah, good catch on OL.

 

[geluso]

Here's photos of the regulator rectifier. Looks to me like it is OEM.

 

[Its been a long time]

Here's photos of the regulator rectifier. Looks to me like it is OEM.

I'm afraid I'm not so familiar with the after 1980 bikes but yes, it looks like the original rectifier regulator. Now you have found a stator or a white wire problem, I'd take the reg/rec off for testing.

White wires can get damaged by the chain run, worth looking for that. Could be white wire damage rather than stator winding damage.

 

[geluso]

Copy that. I'll check white wires and chain.

 

[Its been a long time]

Copy that. I'll check white wires and chain.

Chain runs very close at the front of the sprocket, white wire damage is very common. Stator damage is less common but not unheard of.

Diodes in the rectifier can fail, need to test that too. If you're lucky you only have a white wire stopping you from charging.

Edited to say - I see right at the start you don't have magnetic field at the rotor. Given I think everything checked OK at the rotor, you still have to work out why that's not working. Could mean you're in for a new rectifier and regulator. But let's see how the white wire condition is first.

 

[geluso]

Had a chance to look at the wires to see if the chain had affected them at all. The wire seem well protected and securely far from the path of the chain. Here's some photos.

 

[gggGary]

Cough, chain lube.

 

[geluso]

Cough, chain lube.

lol copy that. hey, at least I can still blame previous owner for now!