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I want to wire a 160 Monza Jr without the battery or lights just to get the engine running. Looking at the wiring diagram, it looks as if I would just attach the black points wire and the yellow stator wire to the positive terminal of the coil. Do I need to do anything with the other 2 stator wires? Does the coil need a negative ground wire? Will this work just to get a spark? Would a battery help? Any info/diagram would be appreciated.

You've got it right- the yellow alternator wire and the contact breaker wire to one terminal of the coil and ground the other terminal- if the rotor is correctly phased on the crankshaft you should get a spark- no need for a battery.
If you want to understand the system better you could do some web searches for 'energy transfer ignition system', the most common term for this scheme. This ignition system has the contact breaker electrically parallel to the ignition coil- the 'battery coil' system has the contact breaker in series. In the ET system the secondary winding generates enough energy to jump the spark gap as the secondary winding is energized- the battery system sparks as the coil is de-energized.
Rick

Thanks a lot. I will be sure to check that out.

This is the schematics from the 160 manual. Maybe it helps, too.