most 3600 2pole generators have a capacitor across the harmonic winding, encapsalated in plastic and prone to failure shaped 1/4 round 2 to 3" long hooked to stator. the rotor has a diode bridge mounted around the shaft, these four diodes must be unsoldered tested and resoldered and reincapsolated unless you have a shop to test rotor as assembled. The cap fails with holes burned in it if not can be checked with a Sencore Z meter or equal, It applies the working voltage to the cap under test and much more real than the typical digital volt ohm meter. Check You Tube- some English guy flashed the field with 2 electric drills one plugged into the generator the other driving the shaft of the first, the first a universal ac dc version trigger locked on, the second chucked up to drive the first. It is common for some one to run engine out of fuel with load on generator this can suck the residual magnatisim out of the generator and lead to your symtoms