The Brazilian great masterminded the Lions' come-from-behind win at the Saputo Stadium after Didier Drogba had put the home side head in just the opening minute of the contest.
Chelsea icon Drogba rocketed home a free-kick from outside the area, which Orlando keeper Joe Bendik failed to keep out, to notch his ninth league goal of the season.
Montreal's lead, however, was short-lived as Brek Shea levelled for Orlando in the third minute with a simple finish after Carlos Rivas' cross-goal ball fell kindly for him.
At 2-1, Bendik produced a brilliant reaction save to deny Drogba from pointblank range to make up for his earlier error.
Six minutes into the second half and Montreal were reduced to ten men when Bush was sent off for upending Rivas in the error, prompting the home side to bring on back-up keeper Eric Kronberg for midfielder Kyle Bekker.
Kaka stepped up to the spot and expertly sent Kronberg the wrong way to take his season tally to eight goals.
As the drama continued to build, Bendik was again the hero when diving to his right to keep out Drogba's penalty on 70 minutes before Rivas wrapped it up when racing onto a lovely ball from Julio Baptista before angling a pin-point effort across Kronberg to make it 4-1 with just over 10 minutes remaining.
The victory sees Orlando move up to sixth position on the Eastern Conference table where they sit just three points behind the Impact after 27 matches.
Check out the highlights below, courtesy of MLSsoccer.com: