de Dycker, who confirmed his fourth pole position of 2009 on Saturday with a dominant performance that saw him fastest in both practice sessions and then peerless in the Qualification Heat, took the lead early in both sprints and was able to animate the many Belgian fans in the crowd with a comfortable speed advantage.
"I was having so much fun out there and it really helped me,” said Ken. “It was not so easy because the track was so demanding and coming up to lapped riders I really had to concentrate. Sometimes I could look around and saw a lot of people cheering so I was waving to them when I could; it was a really nice experience. This was not a simple GP so I am really pleased with the result."
Second overall was Monster Yamaha's Josh Coppins, with 4-2 race results, with LS Honda's Clement Desalle third with 6-3 race finishes. Outgoing champion David Philippaerts had been second to de Dycker in race one, but managed only eighth in race two.
The closest fight at the sharp end of the world championship is now between Philippaerts, Desalle and de Dycker for third. The trio will start the final round just four points apart.
The MX2 title will go down to the wire, although Marvin Musquin will start the season finale with a healthy 22 point advantage over factory KTM team-mate Rui Goncalves after victory at Lierop.
Goncalves beat Musquin in race one, when the Frenchman fought back from an opening lap fall to claim second, but fortunes were reversed in race two when Goncalves fell twice, damaging his right shoulder and leaving him third at the flag.
The Grand Prix of Brazil will be the fifteenth and final round of the championship, in two weeks' time.