Former world champion Jorge Lorenzo has urged MotoGP organisers to cut the top speed of the sport’s new 1,000cc bikes to improve safety, just months after the tragic death of a young rider.

Lorenzo was speaking after three days of testing brought a generally warm reception for the bigger, faster new machines at Malaysia’s Sepang circuit, where Italy’s Marco Simoncelli died in October.

World champion Casey Stoner demolished Valentino Rossi’s 2009 track record, set on an 800cc bike, by nearly a second on Thursday, although his time of 1min 59.607sec will not stand as a new mark because it was set out of competition.

“We are at the dawn of the 1,000cc (era),” Mike Webb, race director with governing body FIM, told AFP.

“The riders enjoy the bike.

“The spectators will surely enjoy the race a lot more and they will be safer and easier to ride.”

But Spain’s Lorenzo, the 2010 world champion with Yamaha, admitted he was uncomfortable riding the bikes at top speed, which can hit 320 kilometres per hour along straights.

“I am not happy on the top speed. We need to reduce the top speed if we want to make it a safe category,” Lorenzo said.

Seven-time world champion Rossi played down any safety concerns. “We can slide and the bike becomes more fun,” he said.

“I like the 1,000cc. This type of engine has better torque and better driveability. For me... the speed will be impressive and I don’t think it will be more dangerous.”

Beginning in 2002, racing was done on 990cc engines, until the 800cc bikes were introduced for the 2007 season.