Williams is determined to make an improved showing on last weekend's performances in Barcelona where they finished a disappointing ninth.
Williams, who has taken on the role of head coach for these summer tournaments with Paul John acting as team manager, said: "We started slowly last weekend, losing 21-19 to Moldova and although we struck back with a good 33-12 win over Ukraine, we then lost to Spain and Portugal, making things very difficult for us.
"After a 17-7 loss to eventual champions Russia on Sunday morning, we improved significantly by the time we got to the final two games of the weekend, beating Romania 35-0 and Georgia 33-12 to win the Bowl final but the boys have to realise that there are no second chances in Sevens and you have to turn it on for every game.
"We are developing a lot of new players in these tournaments, and the beauty of this series is that we have another opportunity to put things right this weekend in Bucharest. The players know they are capable of much more than they showed last weekend and that is what they will be out to prove in the next few days.
"Steve Taylor returns after playing in our first FIRA tournament in Lyon and Steffan Jones is coming in as a young player who impressed in the National Schools Championship - Gemau Cymru - last weekend."
Wales Sevens squad for Bucharest: Owen Williams (capt, Pontypridd), Rory Watts Jones (Cardiff), Richard Smith (Cardiff), Craig Price (Llanelli), Will Price (Aberavon), Justin James (Llanelli), Rhodri Williams (Scarlets), Rhys Patchell (Cardiff), Luke Williams (unattached), Jake Randell (Scarlets), Steve Taylor (Cardiff), Steffan Jones (Ysgol Bro Morgannwg)