Debut of the 2015 Ducati
The biggest news is that the new-all Ducati Desmosedici GP15 will make its debut at Sepang II, the factory team having used a modified version of last year's bike for the opening test.

Andrea Iannone finished with the third fastest lap time on the GP14.3 earlier this month, while team-mate Andrea Dovizioso was second quickest on day two. How much of a step forward will Gigi Dall'Igna's GP15 provide and will it finally solve Ducati's understeer problems?

Seamless Downshifts At Yamaha?
Factory Yamaha riders Valentino Rossi and Jorge Lorenzo are expected to try a new gearbox featuring seamless downshifts (as well as upshifts) for Sepang II.

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Neither rider would confirm the debut, although Lorenzo did admit: "We expect big things for Sepang II."

The hope for the M1 riders is that the addition of speedier, smoother downshifts will aid braking and corner entry. That is where reigning champion's Honda, which have had seamless downshifts for at least a season, are especially strong.

How Many Repsol Hondas?
After handling problems with the 2015 Honda at last November's Valencia test, Marc Marquez and Dani Pedrosa tried three different versions of the RC213V during Sepang I.

Those were: A 2014 bike, the 2015 Valencia bike and a new 2015 bike. Marquez also revealed he had a fourth option that he didn't use.

Both Marquez and Pedrosa seem to have settled on the newest 2015 bike - described as a 'compromise' between the 2014 and 2015 Valencia. However the reigning double world champion also stated he is not yet quicker than with the more familiar 2014 machine.

"I tried the 2014 bike in one run and the lap time was the same," Marquez said at the end of the first test, where he set an unofficial all-time lap record in the morning. "But I must forget [the 2014] because I will use the new one [this season]."

With only three more days of testing after Sepang II, Marquez, Pedrosa and Honda will be hoping to see a clear advantage from the 2015 bike by the conclusion of the Malaysian tests.

Michelin Tyre Test
Michelin is replacing Bridgestone as MotoGP's exclusive tyre supplier from next season.

The extra fourth day of testing at Sepang II will provide the MotoGP race riders with their first chance to try the new 17" rubber being developed by the French company, which left MotoGP at the end of 2008.

Of the current grid only Valentino Rossi, Jorge Lorenzo, Andrea Dovizioso, Dani Pedrosa, Nicky Hayden and Marco Melandri (edit) have previously raced with Michelin MotoGP tyres.

If the feedback from the factory test riders at Sepang I is anything to go by, lap times should be around 1-1.5s from Bridgestone pace. Meanwhile the Michelin front tyre seems to prefer a much smoother corner entry than the Bridgestone.

The race riders will certainly need to approach Turn 5 with care, having been the scene of three fast falls for the test riders.

The Newcomers: Aprilia and Suzuki
Suzuki clearly needs more horsepower, yet that only made tenth and twelfth places on the timesheets for Aleix Espargaro and rookie Maverick Vinales all the more encouraging.

The Japanese factory, returning to MotoGP for the first time since 2011, was forced to halt engine performance development in order to solve reliability issues exposed during the Valencia wild-card and subsequent tests.

That now looks to be behind them, but it remains to be seen how long it will take for power-up parts to reach the race team and what further gains can be made until then.

Aprilia, also returning to MotoGP this season, joined Honda in bringing a second version of its 2015 bike to Sepang I. However the revised RS-GP wasn't well received and riders Alvaro Bautista and Marco Melandri reverted to the machine tested in late 2014.

But development rider Michael Laverty made progress with the new bike after trying some 'radical' set-ups at the Michelin test day. Racing boss Romano Albesiano believes the two versions are now closely matched and it will thus not be surprising to see Alvaro Bautista and Marco Melandri giving it another try this week.