What was found
DURING CRUISE, GEN 1 OFF BUS CAS MESSAGE ILLUMINATED. QRH PROCEDURES FOLLOWED, AIRCRAFT FLEW AT OR BELOW FL310 AND LANDED WITHOUT INCIDENT. REPLACED GEN 1 WITH NEW UNIT IAW IAW EMB 550 AMM 24-31-01. FAILED GENERATOR WAS S/N 1240, WHICH FALLS INTO THE AFFECTED RANGE FOR UNRELIABLE GENERATORS AS IDENTIFIED BY EMBRAER. DISCOVERED CRACKED GEN 1 EXHAUST DUCT ADAPTER. REPLACED GEN 1 EXHAUST DUCT ADAPTER IAW EMB 550 LMM TASK 72-00-60.