Walker made an attempt at the 500 cc World Championship in
2001. He predicted that "For me it's going to be the toughest year ever", which proved accurate, as the factory
Shell-sponsored
Honda was hard to ride and forced Walker to override, resulting in many huge crashes. In , he moved to the
Superbike World Championship, initially with the Fuchs Kawasaki team. Walker placed 6th in the championship for GSE
Ducati in , and 11th for
Carl Fogarty's Foggy
Petronas team in , respectively teamed with
James Toseland and
Troy Corser (both of whom won the title the next season, Toseland riding the Fila Ducati to success and Corser the Alstare Suzuki in ). In , Walker joined the PSG-1
Kawasaki Corse team, proving to be the most consistent Kawasaki rider in terms of pace and results, securing one podium finish (3rd place, round 6 at
Valencia) and finishing 7th place overall. saw Walker teamed up with Frenchman
Régis Laconi and
Spain's
Fonsi Nieto on a Kawasaki Europe backed
ZX-10R for PSG. Walker secured his maiden Superbike World Championship race win on 3 September 2006 in Race 1 at Assen,
Netherlands in his 131st race. Starting the race in 13th position, and dropping to 26th position at the first corner following an excursion onto the grass, Walker braved the torrential
rain and a high rate of attrition to win in a time of 44 minutes, 23.501 seconds. He came 9th overall in the championship, 19 points ahead of Nieto as the highest Kawasaki. Despite his finishing position, Walker was subsequently dropped by PSG for the season, while Kawasaki still supported PSG as an official factory team. ==Return to the British Superbike Championship 2007==