Starting from pole position in the opening dry race, the Rizla Suzuki rider made a steady start, falling back to fifth on the opening lap before battling back up the field. He was always in contention for the victory and set the fastest lap of the race at the 1.41-mile Mallory Park circuit on his way to fourth place.
In the second race, with the track soaking wet but the sun shining, Sykes opted for an intermediate front tyre and slick rear. He got the holeshot but dropped back to ninth before the track dried enough to take advantage of his grippy Pirelli. He scythed through the field as the sun shone and was fourth again.
Team mate Atsushi Watanabe showed real aggression and speed to take ninth in the opening race but found the treacherous conditions in race two difficult, ending up 20th.
Ducati's Shane Byrne won the first race and Michael Rutter the second.
There is now a three-week break for the Rizla Suzuki squad with round seven of the British Superbike Championship taking place at the picturesque Oulton Park circuit in Cheshire on the July 20th.
"Race one was very frustrating. Rather than getting my trademark good start, my clutch grabbed and I found myself sixth going into the first corner. I fought my way up but the guys in front were quick and difficult to overtake. It's a shame as I had the pace and if I'd got off the line better I may have pulled away with a clear track in front.
"The second race was a real lottery and the tyre choice we made was a good balance. As the track dried I got faster and fourth was the best I could do. It was a hard race and I am happy to have brought my Rizla Suzuki home given how slippery the track was during the first few laps. I'll just have to wait to the next round at Oulton Park before I get my maiden win..."
"Race one was not so bad and I have good start and fighting for top 10 positions. This makes me happy and I hope for same for race two but the rain falls and tyres choice tough and many quick riders make very difficult for good result.
"The racing today has been up and down and I am still learning. I will think on this and come back stronger and for more top 10 places at the next round."
Jack Valentine - Rizla Suzuki Team Manager:
"I was a bit disappointed for Tom in the opening race because he had the pace to win but got a very uncharacteristic poor start. He was the only rider to go under 56 seconds a lap and that shows just how close we were to winning.
"The second race was a real gamble on tyres and Tom's crew made a sensible choice. It was exciting to watch and he thoroughly deserved another fourth place finish and the points in the bag for the Championship.
"Atsu put on a brave battling performance in the opening race but the conditions hit him hard in the second. He has the talent, team and bike to compete at the front and we'll be doing all we can to get him up where he belongs during the second half of the season."
Race One Result:
1: Shane Byrne (Ducati) 28:33.049
2: Leon Haslam (Honda) +1.024
3: Cal Crutchlow (Honda) +1.147
4: Tom Sykes (Rizla Suzuki) +1.355
5: James Ellison (Honda) +11.302
6: Billy McConnell (Kawasaki) +17.149
7: Simon Andrews (Yamaha) +18.252
8: Tristan Palmer (Honda) +19.761
9: Atsushi Watanabe (Rizla Suzuki) +26.422
10: John Laverty (Ducati) +27.593
Race Two Results:
1: Michael Rutter (Ducati) 30:10.219
2: Shane Byrne (Ducati) +4.405
3: Cal Crutchlow (Honda) +4.586
4: Tom Sykes (Rizla Suzuki) +13.383
5: Karl Harris (Yamaha) +13.589
6: Leon Haslam (Honda) +19.517
7: Simon Andrews (Yamaha) +25.928
8: Leon Camier (Ducati) +35.007
9: Tristan Palmer (Honda) +44.194
10: Scott Smart (Kawasaki) +56.422
20: Atsushi Watanabe (Rizla Suzuki) +2 laps
Championship Standings (after round six of 12):
1: Shane Byrne 280
2: Cal Crutchlow 183
3: Leon Camier 160
4: Leon Haslam 148
5: Michael Rutter 127
6: Tom Sykes (Rizla Suzuki) 126
7: James Ellison 119
8: Michael Laverty 84
9: Simon Andrews 69
10: Stuart Easton 62
15: Atsushi Watanabe (Rizla Suzuki) 30