Completing a day of 186 without a loss, India enjoyed another batting display in which both the openers turned their innings into centuries.
Raichandani remained unbeaten on 196 off 306 balls, smashing four fours and three sixes. He bats alongside Kush Patel, who has not conceded three at the end of the game.
Sagar Virk is also a century
Raichandani got excellent support from fellow opener Sagar Virk, who scored a patient 134 from 312.
The opening pair laid a solid platform for India before Virk departed after his century.
India are left with 46 runs
At stumps, India U-19 were 378/3, trailing Sri Lanka U-19 by 46 runs.
The hosts had already posted a declared 424/9, thanks to a brilliant two-year spell from Senuja Wekunagoda.
The game is being played in Galle
The Youth Test is being played at the Galle International Stadium, the venue for the first Test between senior teams India and Sri Lanka next month.