Jeremy McWilliams experienced an eventful RS Cube debut at Valencia today (Friday), the Ulsterman falling from his new Aprilia as he acclimatised to the three-cylinder machine.

As well as his harmless - but no doubt embarrassing - accident, McWilliams also made several unplanned trips off track during his 60 laps, as the notoriously twitchy prototype bit back at its new owner.

The former Proton KR rider went on to set a best time of 1min 37secs - 1.5secs behind his fastest race lap from the season ending Valencia Grand Prix on the KR V5, but Jeremy openly admitted he was a little rusty after almost three-months away from action.

Meanwhile, on the other side of the garage, team-mate - and MotoGP rookie - Shane Byrne (lower pic) continued his steady progress as he knocked a further 0.2secs from his fastest Valencia test lap, putting him within 1sec of Colin Edwards' best from the GP.

Joining the MotoGP riders were factory Aprilia 250cc pilots' Manuel Poggiali, Sebastian Porto and Fonsi Nieto - Porto would surprise by setting the pace, lapping some 0.4secs faster than reigning world champion Poggiali, with Nieto a further 0.6secs adrift.

Testing concludes tomorrow (Saturday).

Aprilia Valencia test - day one:

1. Shane Byrne GBR Aprilia 1min 35.1secs
2. Jeremy McWilliams GBR Aprilia 1min 37.0secs

Comparative lap times:

2003 Valencia Grand Prix:Pole Position: Valentino Rossi ITA Repsol Honda 1min 32.478secsFastest Lap: Valentino Rossi ITA Repsol Honda 1min 33.317secsFastest Aprilia Lap: Colin Edwards USA Alice Aprilia 1min 34.292secs

Best pre-season Valencia test lap:12/12/2003 Max Biaggi ITA Camel Pramac Pons 1min 32.8secs

For pictures from the Aprilia test - updated daily - click on the "Latest Pictures" link in the MotoGP channel...