Continuing his dream run Uthappa played the sheet anchor role in his unbeaten 83 from 51 balls (10x4, 1x6) in a 121 runs partnership from 70 balls with Shakib Al Hasan (60 from 38 balls; 5x3, 3x6) to help KKR post a towering 195/4.
This was Uthappa's fifth half-century this season as with a tally of 572 runs, the KKR opener usurped the Orange Cap from Glen Maxwell (533), who was holding on to the pole since the start of season seven in Abu Dhabi on April 16.
After Umesh Yadav gave the breakthrough in Chris Gayle (6) who got out to a dubious lbw decision, Yogesh Takawale and Virat Kohli kept RCB in the hunt in their must-win match with an 85-run partnership but Narine struck twice in his third over scalping both the dangerman to keep them in check.
He returned the same way in his fourth over this time claiming another two prized sclaps of Yuvraj Singh (22) and AB de Villiers (13) to turn the match around.
KKR were reduced to 56/3 in the seventh over at the sun bathed Eden Gardens after Virat Kohli put the home team up front but Uthappa defied the heat to take the attack to the opposition.
Shakib Al Hasan played a perfect ally and was more brute at the other end as the Bangladeshi all-rounder spanked 38-ball 60 and the duo put together 121 runs from 70 balls for the fourth wicket to stage a remarkable recovery against a frail RCB bowling attack.