The final day of this week's private Sepang MotoGP test saw Ducati unveil yet another technical development, and Yamaha appear with white wings on their M1.

As on the previous two days, a damp track delayed the start of testing - and was followed by an afternoon rain storm.

In between the MotoGP test teams present - from all six manufacturers - got their final chance to check their machines in the dry, prior to handing them to the race riders in next week's official test.

Ducati - which caused a stir on Wednesday with a mysterious new black ('salad') box under the tail unit of the GP17 - again rolled-out visible new developments on Friday.

This time, Michele Pirro appeared on track with 'lenticular' wheel covers. The Italian had briefly tried a similar (more extreme) version on the rear wheel during last September's Misano round, but this time they were fitted front and rear (see picture).

At Misano, Ducati had said the covers were 'for the evaluation of aerodynamics'.

Rain or not, Pirro is heading back out. pic.twitter.com/Yk7mEETf1q-- Peter McLaren (@McLarenMotoGP) January 27, 2017

Pirro also rode with special sensors fitted to his Ducati, which created a small beam of light under his bike, presumably to measure chassis and/or tyre movement.

Star test rider Casey Stoner was also on track today, but seemed to be troubled by technical issues, stopping twice at Turn 12. Both Stoner and Pirro are expected to ride at some stage during next week's test.

Wings may be banned in MotoGP this year, but Nakasuga is currently testing with some white ones on his M1. #SepangTest #MotoGP pic.twitter.com/QurYhKf91u-- Crash.net MotoGP (@crash_motogp) January 27, 2017

Over at Yamaha, Katsuyuki Nakasuga had some white wings fitted to his M1, despite the ban on such devices for 2017. Ducati have also occasionally put the devices back on, in order to better understand how to adapt the set-up for a wing-free future.

Hiroshi Aoyama (Honda), Mike di Meglio (Aprilia) and Mika Kallio (KTM) were again on track, while the first of the race teams also began to arrive and set-up their pit garages for next week.

As well as the MotoGP teams, Honda, Yamaha and Suzuki and Moriwaki superbikes are also present. The circuit remains open for wet weather testing, with the likes of Kallio and Pirro still out on track.