Alternator connector at the bottom, with yellow leads should have 3 wires, mark them A,B,C and at about 1500-2500 RPM they should read 50VAC. Since the alternator is a 3 phase machine. Most usually replace the connector and solder the wire together. Readings as follows: A-B=50VAC, A-C=50VAC, B-C=50VAC. Once reconnected rev to 1500-2500 and verify that the voltage to the battery is 14.8 VDC with a partially discharged battery.
Higher rev missing, could be points too far apart, low fuel as in dirty filter, low voltage on primary spark side thus low volts on plugs, posibly become cured when battery voltage returns to normal at 14-15 vDC.