DF4 3650 was one of a batch of DF4Bs rebuilt with the more powerful "D" series engine used in the DF4D. The loco was photographed working an eastbound freight east of Dachengzi on the Miyun - Chengde line on 27 September 2006. The DF4BDs received the same blue and cream livery carried by DF4Ds but a number of "straight" DF4Bs built by Ziyang in recent years received the same colours, so it can't be taken as a foolproof indication that a loco is a DF4BD.