The New York Rangers grabbed a 2-0 lead in the First 6 1/2 minutes of tonight's hockey game and thoughts of champagne and $17,000 winners' checks danced through their heads. Then the Montreal Canadiens picked their pockets.

Sweeping past the bewildered Rangers with the speed that earned their forefathers the nickname Flying Frenchmen, the Canadiens breezed to a 6-2 victory and tied this Stanley Cup final at a game apiece.

There were no passengers on the Bleu, Blanc et Rouge express tonight, as everyone contributed to the remarkable comeback. Even goalie Ken Dryden, after blowing two of the Rangers' first three shots, had earned applause from the 17,024 Forum critics by game's end.

Dryden was starting one again because Bunny Larocque was dealt a rabbit punch by fate. Larocque had waited five years to start a Stanley Cup game and tonight, just before the warmup, trainer Eddy Palchak handed him the ceremonial puck.

But in the last minute of the warm-up Larocque was struck on the forehead by a Doug Risebrough blast of such velocity that it cracked Larocque's helmet. So instead of that long-awaited start, Larocque spent the game-and the night-in a hospital with severe headaches and nausea.

Defenseman Serge Savard, one of the Canadien's 40-minute men, had spent 24 hours fighting the flu, had finally eaten a modest meal this afternnon and was uncertain what contribution he could make.

When the Rangers' first shot, a fairly routine effort by Anders Hedberg from the right-wing circle, sailed over Dryden's right shoulder, the Canadiens were in deep trouble.

At the other end, Ranger goalie John Davidson made a tough stop of Jacques Lemaire's deflection of a Rick Chartraw drive and Guy Lefleur could not lift the rebound into the net. Then Davidson foiled Lemaire's breakaway and, sitting in the crease, swept the rebound away from Lafleur.

The play moved into Montreal ice and the Canadien's Brian Engblom deflected a Mike McEwen slap shot onto the stick of Ron Duguay. His 30-footer popped into the net off Dryden's stick and it was 2-0.

"I was scared a bit," Savard said. "We had outplayed them and still the score was 2-0 for them. They had the hot goaltending and noting was going right for us."

The luck changed when Montreal's Mario Tremblay fired a pass from the right-wing boards toward Yvon Lambert, skating down the slot with two Rangers clinging to him. The puck struck Lamberths skate and skipped past Davidson.

Lafleur, given another rebound after Davidson stopped Lemaire, this time lifted the puck over the goal-tender for his 10th playoff goal and the score was even.

Before the period had ended, Bob Gainey broke down the slot after taking a breakaway pass from Doug Jarvis and drilled a 20-footer through Davidson, Montreal was ahead to stay.

"We were tight at the beginning and it was a bizarre first period, counting the warmup and five goals," said Montreal Coach Scotty Bowman. "To come out of it ahead by a goal gave our club a big lift."

Steve Shutt's steal from Phil Esposito and subsequent score as Mario Marois knocked Shutt, Davidson and the puck into the net, made it 4-2. Davidson blew a short-side 45-footer by Lemaire and Mark Napier wrapped up the scoring on a two-on-one break with Gainey.

Even more pleasant for the Canadiens than the six goals was the fact that they used six defensemen successfully, in the absence of Guy Lapointe. Chartraw and Gilles Lupien performed capably along with Engblom adn Rod Langway as the ailing Savard and Larry Roninson were given less work thatn usual.

Dryden said he was neither surprised nor upset to be apssed over for the starting assignment, but found it difficult to calm himself once he was called upon.

"I was trying too hard and I had to tell myself to relax," Dryden said. "There was 55 minutes to play and I knew we could still get enough goals to win. Even if you don't get one for 10 minutes, you just have to play your game. You can't panic and we didn't."

The third game of the best-of-seven series will be played in New York Thursday. CAPTION: Picture, Doug Jarvis of Canadiens takes out Ranger goalie John Davidson. UPI