Day two of private testing at Sepang saw Honda unveil a new design for their 'downforce' fairing.

HRC, which used a relatively modest wing-fairing in 2017, looks to have followed the precedent set by Ducati and Aprilia, with test rider Hiroshi Aoyama taking to the track with a clear 'box' shape on either side of his RC213V (left and middle pic).

However, the vertical plane linking the two horizontal surfaces is not solid, but has a large tri-angular cutaway.

Meanwhile, with MotoGP Technical Director Danny Aldridge saying changes would be needed to the radical Yamaha 'wing' seen at November's Valencia test, has the factory responded with a slightly revised design?

It's hard to tell, but from some angles it looked like the Sepang test bike of Katsuyuki Nakasuga (right pic) has a smoother, swept-back design, with a slightly bigger gap between the upper and lower 'wing' surfaces than at Valencia...

Either way, the Yamaha certainly has more of a triangular shape, compared with the 'box' on the Ducati, Aprilia and Honda.

Teams can use any fairing design they wish for testing, but those used in grand prix weekends must be passed by the Technical Director.

Ducati have been testing their GP18, in the hands of Casey Stoner and Michele Pirro, without any wings so far this week while KTM and Aprilia have been using their end-of- 2017 designs.

UPDATE: Some more technical tweaks seen on track by the end of day three. The different Ducati hub is thought to be a new design for the torque sensor, but the frame also has several clear changes compared to the launch bike (assumed to be a GP17).

Different rear sprocket/hub for Ducati at Sepang this week, compared with the launch pictures of the GP18...#SepangTest #MotoGP pic.twitter.com/RZyuyxrXj9 — CRASH.NET/MotoGP (@crash_motogp) January 26, 2018 You've seen the Honda hammerhead and here is what looks to be a new Yamaha fairing. While hard to fully appreciate in 2D, it resembles a twisting ribbon as it flows backwards to the lower mounting point. Rossi and Vinales could well try it in a day or two.#SepangTest #MotoGP pic.twitter.com/ublIAm2KYK — CRASH.NET/MotoGP (@crash_motogp) January 26, 2018

Just spoke to Danny Aldridge about the new Yamaha aero package shown here. He said Yamaha have made a lot of changes he requested, but hasn't had a proper look yet. His first guess is it will probably be OK, with tweakshttps://t.co/pTM3LyfjMX — David Emmett (@motomatters) January 27, 2018