MADRID, Spain - Marc Marquez is aiming to become the youngest ever MotoGP champion at the age of 20 as the Spaniard takes a 13-point lead over compatriot and defending champion Jorge Lorenzo into the season's final Grand Prix in Valencia this weekend.Marquez has seen his lead whittled down by a late season charge by Lorenzo but will seal the title in his maiden year in MotoGP should be finish fourth or better at the Ricardo Tormo circuit.The Honda Repsol rider remains very much the favourite for the championship having only failed to make the podium once this year, when he was disqualified for failing to pit in time for a mandatory change of tyres in Australia in October.BLISTERING RUN OF WINS"I am desperate to get back on the bike," he told Spanish sports daily Marca. "We know what is in play in this last GP of the year but will face it as we have in all the other races. We will work hard from Friday and we will do our best."After a blistering mid-season run of four straight wins that put him in charge in the championship standings, Marquez has won just one of the last six races and suffered a heavy crash during practice at Motegi in Japan last time out. However, he's counting on the positive experience of winning the 2012 Moto2 race in Valencia to see him over the line."It's been good to spend a few days at home after three weeks away. Since the fall in Motegi I 've been doing muscular rehabilitation on my neck and now I feel much better. We've had good performances in Valencia before. The weather will be a factor because it is very changeable."LORENZO: 'WE HAVE A CHANCE'Lorenzo had seemed to be out of the championship since a broken collarbone forced him to miss the German MotoGP and affected his participation in the Dutch and American races but four wins in the last six races have given him hope of a third World title and he insists the pressure is all on Marquez this weekend."I'm very stimulated because three races ago we thought the championship was over," said the 26-year-old Yamaha rider, whose only win in the race was in 2010. "Instead we've a chance. Valencia is my home race and it will be very emotional considering our position in the classification."We don't have anything to lose but everything to win and this card plays on our side. Maybe our main rival can feel much more pressure in Valencia than us because he is so close to victory. You never know what can happen, especially if the forecast is uncertain, as it was in 2012."We trust in ourselves and expect a good race in front of our fans. We will never give up!"THREE-TIMES RUNNER-UPMarquez's Honda team mate Dani Pedrosa will definitely finish the season in third place behind his two compatriots but has enjoyed the most success at Valencia with six victories in total, three of them in MotoGP in 2007, 2009 and 2012.And the 28-year-old three-times championship runner-up could do Marquez a huge favour if he manages to keep Lorenzo off the top of the podium with another victory on Sunday.