Wing Nick Reynolds will sit out the clash with the Canucks with an abrasion to the leg, and is replaced by Carmarthen Quins' Jamie Davies who has recovered from a hamstring injury.
Squad captain Scott Andrews returns to the 22 after recovering from a back twinge, as does Dragons Academy and Ebbw Vale fly-half Dai Langdon who picked up an ankle injury in the pre-tournament development game against Japan.
Davies said, "This next game is vitally important for us not only in this competition but also for qualification to Argentina next June. We were thrilled with the performance of the team against Tonga, the forwards laid a great platform and the backs were able to express themselves in attack. The new caps also did themselves no harm at all and we have gone for consistency in selection ahead of this second game.
"The Canadians will provide a very physical challenge so it will be very important to front up to that and dominate the contact area, enabling us to provide quick ball for our backs to play with width.
"Other than Nick Reynolds, who should be available for selection for Australia on Saturday, we have a fully fit squad and it's great to see Scott Andrews and Dai Langdon back in the 22, they have worked incredibly hard to get back to full fitness under the guidance of Wayne Proctor and are looking forward to their first experience of world cup rugby in Japan.
Canada lost 86-0 to Australia in their opening match but captain Harry Jones is confident his side can step up their performance level.
"We expected them (Australia) to be a very good side and it was going to be tough," admitted the University of British Columbia student. "We played well in the first 25 minutes against a fully professional side but the Australian back line is quite unbelievable. We are going to learn and step up from that.
"Obviously we have to get our defence skill a lot better and offensively getting more possession to attack with the ball. With the changes we have made, we should be going in the right direction now."
In last year's inaugural Junior World Championship held in Wales, Canada finished 12th after a tough pool experience - having again met and lost heavily Australia in the opening match, they lost to eventual runners-up England before beating Fiji.
Coach Tim Murdy insisted that the experience of last year is an example for the 2009 squad to follow and that his charges need to focus on their progression though the Championship, despite the result of the first match.
"Right now our full focus is on our process and trying to do things properly," said Murdy.
"In terms of thinking about beating Wales and Tonga we are paying a lot of attention to our set pieces and making sure we hold onto the ball. We also need to put them under a lot of pressure with our defence."
Wales Under 20 v Canada Tuesday 9 June, 11am UK time:
Daniel Newton (Scarlets academy/ Llanelli); Jamie Loxton (Blues academy / Glamorgan Wanderers), Jason Harries (Carmarthen Quins), Ashley Beck (vice-captain, Ospreys academy / Aberavon), Jamie Davies (Carmarthen Quins); Matthew Jarvis (Ospreys academy / Neath), Lloyd Williams (Blues academy / Glamorgan Wanderers); Aaron Coundley (Dragons academy /Ebbw Vale), Rhys Williams (Blues academy / Pontypridd), Simon Gardiner (Scarlets academy / Llanelli), James King (Ospreys academy / Aberavon), Ashley Sweet (Dragons academy / Cross Keys), Justin Tipuric (capt, Ospreys academy / Aberavon), Rhys Jenkins (Dragons academy / Ebbw Vale), Rory Pitman (Ospreys academy / Bridgend / Taranaki)
Replacements: Scott Andrews (Blues Academy / Glamorgan Wanderers), Craig Attwell (Dragons academy/ Newbridge), Dan Partridge (Cardiff) James Thomas (Dragons academy / Ebbw Vale), Rhys Downes (Blues academy / Pontypridd), Dai Langdon (Dragons Academy / Ebbw Vale) Scott Williams (Scarlets academy / Llanelli)
Wales Pool D fixtures (all at Best Amenity Stadium, Saga):
Wales 51-5 Tonga Friday 5 June
Wales v Canada, Tuesday 9 June
Wales v Australia, Saturday 13 June