By Jonathan Stempel NEW YORK (Reuters) – Justin Chimienti thought the Big Mac he bought at McDonald’s and the Bourbon Bacon Cheeseburger he bought at Wendy’s would be as big and juicy as advertised. He says they were not, and now he is suing the fast-food chains. Chimienti sued McDonald’s Corp and Wendy’s Co on Tuesday, accusing them of defrauding customers with ads that make burgers appear larger than they actually are. The proposed class action filed in Brooklyn federal court is similar to a lawsuit filed in March, by the same three law firms, against Burger King Corp in Miami. Chimienti sai…