Jinma starter solenoid disassembly

Problems with my 254 Jinma starter this week was a learning experience.
I found an old discarded starter solenoid that only occasionally worked (about one out of ten times).
I decided to disassemble it.
To remove the black plastic cover only requires unsoldering the electromagnetic coil leads. The battery/starter motor leads in that black plastic cover can remain in place.
Desoldering requires a vacuum source or some way to wick away molten solder. I used a small wire brush to sweep it away (wear goggles/safety glasses).

Once the leads are free the cover will lift off. What I found was bad quality control (typical Chinese at this point).

There is two electromagnetic windings in this solenoid. Technically a primary and secondary winding to enhance the electromagnetic forces. That means there are 4 wire ends. Those 4 wire ends are then solder together creating 2 wire leads that are soldered to the outside of the black plastic cap.

On my solenoid there was only 3 leads. The 4th lead was laying loose under the plastic cap and never connected. Soldering it to the 2nd lead allowed both electromagnetic coils to energize and work consistently once the black cap is reinstalled.
To test it you will need a sufficient voltage source and the iron core that comes with it. My weak 10 volt car battery was not sufficient ,so 12 volts is important,( a 40 amp boost battery charger should also be sufficient.
Then energize the two soldered joints
In the cap while the iron core is installed to get a forceful magnetic reaction.