Repsol Honda rider Stoner leads the factory Yamaha of Lorenzo by 20 points after defeating his title rival last time out at Laguna Seca in the United States.
With eight races to go, including Sunday's at Brno in the Czech Republic, Lorenzo needs to make sure Stoner does not increase the points gap.
Lorenzo said: "After the long break we are going to Brno completely recharged and ready to fight and try to reduce the gap with Casey."
The Spaniard knows the track well having won the MotoGP race there last year and also having recorded wins in the 125cc and 250cc classes.
He said: "This is a track I like and where I won last year. I hope we can start the second half of the season on the podium."
Lorenzo spent the mid-season break relaxing in the Dominican Republic and has renewed focus on what lies ahead, including a day testing his 2012 race machine.
Yamaha are gearing up for the switch from 800cc to 1000cc engines next season and Lorenzo is looking forward to the change.
He added: "After the race we will be testing the 1000cc bike for one day. I am really looking forward to discovering the new Yamaha."
Stoner's team-mates Andrea Dovizioso and Dani Pedrosa lie third and fourth in the standings ahead of multiple champion Valentino Rossi who is still struggling to come to terms with the factory Ducati following his move from Yamaha.
Lorenzo's team-mate Ben Spies lies sixth in the table ahead of Rossi's team-mate Nicky Hayden and the Monster Tech 3 Yamaha of Colin Edwards.
San Carlo Gresini Honda duo Hiroshi Aoyama and Marco Simoncelli round out the top 10, with the latter still looking for his first podium finish in MotoGP despite setting pole position and leading races this season.