Q:
Champion Loot Bags
A:
As a general rule, Magic Find does not affect drops from bags. The exception are bags that are meant to replace the loot you would normally get from enemies, such as from PvP or in the Personal/Living Story. So, no, Magic Find does not affect loot from Champ Bags.
Having a high MF doesn’t hurt though.
http://wiki.guildwars2.com/wiki/Magic_find
It doesn’t affect the loot of the champion bag, though it can affect it’s rarity.