Ben Spies needed only minor changes to the mechanical set-up of his 1000cc Yamaha to finish in fourth place during this week's Sepang MotoGP test.

The 2011 Assen winner left the first of the two Malaysian tests 0.888sec behind Honda's world champion Casey Stoner - but less than three tenths from team-mate and top M1 rider Jorge Lorenzo, in second.

"It was a good day," said Spies. "We worked more with the bike, back-to-back testing a couple of different set-ups and some weight distribution."

Spies revealed he has only just scratched the surface in terms of adjustments for the new M1 which, at present, looks a much closer match for the factory Hondas relative to last year's 800cc machine.

"I can honestly say, this whole test all we changed were the front spring and the rear spring. Geometry wise we didn't touch anything," he said.

"We did do a lot of work with just the electronics. Fine tuning it, because it's definitely different with the 1000. Then some tyre work for Bridgestone.

"I also tried the Yamaha test rider's bike which had a slightly different set up to make a fair comparison with mine. I made a small mistake, losing the front [and falling] but that's testing!"

Like Lorenzo, Spies is hoping for further electronic developments to smooth out power delivery in time for the next Sepang test at the end of this month - but added that Yamaha has much bigger modifications in the pipeline.

"You never know [Yamaha] could show up with another swing-arm, chassis and engine. They say they are working on everything. It's just the timing," he said.