Ben Spies, who finished the first Sepang test 1.341sec behind fellow Yamaha rider and reigning seven time MotoGP champion Valentino Rossi, cut the gap down to 0.775sec during the first day of the second Malaysian outing.

The reigning World Superbike champion and grand prix rookie worked on revised geometry settings to improve rear grip on his Monster Yamaha, helping him shave 0.423sec off his best time from just three weeks ago.

To put that into perspective Rossi, although once again fastest, was slightly slower than he had been at the first test, while second fastest Casey Stoner (Ducati) went only 0.101sec quicker.

"It was hot out there today but I'm happy with how I performed and I feel I've accomplished a fair bit," said Spies. "I automatically picked up where I left off here because my fourth lap today was only three-tenths slower than my best time at the first test. I'm close to half-a-second faster than the last test and I'm more consistent.

"My fastest laps were all on tyres that had done race distance and that makes me happier than anything else," he revealed. "It's not so much that I got under the 2.02 barrier but I did it on worn tyres and I think that will be one of my big strong points this season. I feel like I'm getting closer to finding the limit of the Bridgestone tyres and I'm getting more comfortable on them, but we still need to do more work.

"Today we played around with the bike a bit more than previously just to understand a few things but it was nothing major. Some changes were good and some were bad and I feel we made some important progress and I definitely had more grip. Everyday I'm trying to learn something and go a little bit quicker and that's what I achieved."

Spies was also the top satellite rider, although just one place and 0.054sec behind him was team-mate Colin Edwards, who just dipped under his first test best despite a technical issue costing him precious track time.

Once out on track, Edwards worked on a new swingarm while also evaluating new electronics.

"After the small problem I had this morning I had to play catch up pretty quick to the rest of the guys but I managed to do some good laps and I'm happy with my pace," said the Texan. "It was a productive day and I feel like we've learned a few things.

"Everybody is testing electronics and Yamaha have done another good job because what I tried definitely has some good points and they are moving in the right direction. Yamaha might have dominated last year but they definitely haven't just taken the easy option and sat back. They've worked really hard on improving what was already a great bike, and some of the improvements have really helped me.

"I did more work on the new swingarm and I like it. It seems to help the front and the rear of the bike and it gives me a lot more confidence. And it helps a lot with my front feeling, which I had an issue with a bit last year."

Testing at Sepang concludes on Friday.