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Get a suitable Variac or equivalent, and ac ammeter. Primary only, no load on secondary.
Measure and plot current vs voltage from about 90 to 130 volts. Maybe start lower if there is an internal short. As you raise voltage stop and remove voltage if current rises rapidly.
A nominal maximum hot spot ( meaning internal, not the surface ) temperature should be less than 100 deg centigrade for 105 deg C wire. If higher temperature wire (meaning insulation rating) was used in the transformer design the design point would be higher.
You could be going heavily into core saturation ( should not be ) or have shorted turns.
Certainly the unloaded input current should not approach full load current.