What was found
AT 40000 FT STRONG BURNING ODOR COMING FROM COCKPIT & CABIN. ODOR DISSIPATED ON ITS OWN AFTER APPROX 5 MINUTES. NO EICAS MESSAGES, PACK SUPPLY TEMPS BOTH AROUND 120. CHECKED APU OIL & SYS IS FULL. STARTED APU & TURNED ON BLEED AIR. OPENED ALL VENTS IN COCKPIT & CABIN, CHECKED FOR ANY ODOR AFTER 30 MINUTES OF RUNNING. ALL SYSTEMS CHECKED GOOD IN ACFT 7 DID NOT NOTICE ANY BURNING OR UNUSUAL ODOR. STARTED LT & RT ENGINES & CHECKED ALL SYSTEMS FOR PROPER OPERATION & ALL SYSTEMS OPERATIONS CHECKED GOOD. RAN ENGINES FOR 15 MINUTES WITH NO EICAS MSGS & NO BURNING ODOR.