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75 DT125 Not Charging

Had a lot of issues in both bar switches, key switch, starter solenoid and wiring in the headlight bucket all which are now corrected.


Set timing with a dial indicator. Runs Great. Just not charging.

Armature/Commutator ohm out correctly at 5.and not shorted.

New brushes in stator.

Stator shunt field coil (F to A) ohms out at 4.9. Calls for 4.9-5.8.

Stator series field coil (M to A) Ohms out at .2. calls for .013-.014.


Starter turns over but slow.

Not hearing any clicking at regulator when trying to start.


Had already cleaned up commutator and undercut mica.


Picked up another known good regulator, no joy.


Took off the 72 AT125 timing cover, removed wires off stator and Ohm'd it out for comparison and got the same as the 75.


All I can think is bad ground and not getting power from regulator to energize field coil.


Your thoughts?


Thanks in advance,

Richard

177 Views
Shyted
Shyted
Sep 17, 2025

Hi Rich.

Try running an earth cable to the motor see what happens, and also how's the battery? My AT 1 had the following symptoms.

Would start on the button after Struggling to turn over then started.

Horn wouldn't work at all.

Lights dim.

Neutral light pretty good.

Then nothing on the button to start.

It would start by kicking.

10.9V at the battery terminals, ignition on dropped to9.7V, hit the button 4V.

Acid level okay.

Whipped the battery off and trickle charged for 30 hrs ish. Re fitted all problems vanished. Just starts instantly not even spinning over.

Just an idea or two chief.

Shyted


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