Spain's Jorge Lorenzo dominated Friday's combined free practice on his Yamaha despite hazy weather conditions ahead of this weekend's Malaysian MotoGP.

The two-time world champion outperformed Italy's Valentino Rossi by setting a blistering pace at the 5.5-kilometre (3.4-mile) Sepang International Circuit track, and in punishing heat, posting a best lap of two minutes 00.246 seconds.

Deploying extreme lean cornering techniques, the 28-year-old Lorenzo was 0.669sec ahead of team-mate Rossi, the championship leader who hopes to win his 10th career world title in Sunday's Malaysian GP at Sepang.

"We have a good bike and with good riding we can do well in the two remaining races," a smiling Lorenzo told reporters after the practice.  

"I have a good feeling in Malaysia. Let's see, the best rider will win the championship," he added.

Challenging closely were Honda riders -- Spain's Dani Pedrosa was second quickest, at 0.047sec off the pace -- while team-mate and defending world champion Marc Marquez, who won in Sepang last year, was third fastest at 2:00.472.

Italian Ducati rider Andrea Iannone was fourth, but was 0.240 down on Lorenzo's time while Rossi was fifth fastest at 2:00.915.

- Marquez dismisses Rossi -

Meanwhile, Marquez who won at Phillip Island last weekend rubbished Rossi's allegation on Thursday's that he helped his title rival Lorenzo in the Australian race by making it difficult for the Italian to beat Lorenzo.

"I am surprised like everybody (by the allegation). I won in Australia and will try to win in Sepang and Valencia. I overtook Lorenzo on a difficult downhill to win. Only Valentino knows why he is attacking me," he told reporters after the practice.

Lorenzo also ruled out Rossi's claims.

"No. No. I was leading 80 percent of the race. Marquez was not helping me in the race," and described the sensational young Honda rider as "super talented, aggressive and ambitious."

Only Rossi and Lorenzo can win this year's MotoGP crown as it heads into the two final rounds of the season.

Adding to the drama, crowd favourite Rossi only holds a slender 11-point lead at the head of the championship table over his old rival Lorenzo.

A classic battle erupted between the two Yamaha riders to top the timesheets during the morning practice but a calm Lorenzo managed to dominate both sessions.

In order to win the title in Malaysia, the 36-year-old Rossi will need to increase his lead in the championship to at least 26 points.

Rossi, the oldest rider in the MotoGP entry list, risks a world title showdown in the season's final race in Valencia on November 8 if he does not grab the title in Malaysia.

If Rossi goes on to capture the crown this season, the Italian will be the second eldest title winner since the world motorcycle racing championship started in 1949, when 38-year-old Briton Leslie Graham won the inaugural 500cc crown, race officials said.

Sepang is one of the season's most demanding circuits but is also Rossi's favourite track as the Yamaha racer has won six times here in the premier class.

Temperatures can soar well above 30 degrees Celsius at the circuit, which lies outside Kuala Lumpur and is one of the longest in the season.
Source: AFP