Two third-period goals by Guy Lafleur runined an outstanding effort by the Washington Capitals tonight and carried the Montreal Canadiens to a 2-0 victory, their 11th shutout in a 34-game rivalry that has yet to show a Captial success.

Washington had a 32-25 edge in shots but got nothing past goalie Michel Larocque, a much-criticized figure playing only because regular Denis Herron has a bruised collarbone.

Goalie Gary Inness, defensemen Leif Svenson and Rich Green, and center Guy Charron were standouts for a Washington team that proved for the second time in a week that it need not be embarrassed to match up with the Stanley Cup champions.

The breakthrough came early in the third period, as Washington's Robert Picard fell at center ice when Montreal's Larry Robinson sent the puck toward the Washington zone. Lafleur raced past the helpless Picard, scooped up the puck and beat Inness with a backhander.

"I was going the other way and then the puck was coming back and I turned too quickly and went down," Picard said. "I guess I've got too many feet and I got tangled up in them."

With barely more than three minutes to play, Lafleur made it 2-0 with his 14th goal. Robinson, playing at left wing, carried the puck down the middle and was ridden off by Gord Lane. The puck lay in the slot as Green, also tyring to cut down Robinson, wound up interfering with Inness.

Lafleur swiftly skated in unchecked and drilled the puck into the virtually empty net. Lafleur now has collected at least one point in 11 straight games, but he saw nothing to celebrate tonight.

"I don't know why we are trying to match lines and play so defensively," Lafleur said. "That is fine in the playoffs, but against a team like Washington right now we should be trying to score."

The Capitals, although concentrating on defense, tried hard to beat Larocque. The closet call came with the score 1-0 when Mike Gartner took Bengt Gustafsson's perfect pass and drilled a shot off the crossbar. It was the sixth time Gartner has struck iron instead of gold.

"Maybe I'm trying too hard to get a good shot, shooting too fine," Gartner said. "I've got to start capitalizing, concentrate more on putting the puck between the posts. Things just aren't going my way."

The knowledge that they had played well against the defending champions offered little consolation for most of the Capitals.

"When are we going to stop saying, 'We should have beaten this team'?" wondered Yvon Labre, who has been trying in vain for six years to celebrate a victory over Montreal. $"One day it's going to be our turn," said Ryan Walter. "We haven't lost hope. We had a bit of a get-together this morning and decided that we'd play our best and if we win, we win and if we lose, we lose. But I didn't expect to lose."

"I'm disappointed that we had opportunities and couldn't put them in," said Charron, whose two-way effort earned Belisle's praise. "If we'd capitalized on our chances, we'd have had a more complete effort. I'm happy with our line (Charron, Errol Rausse and Mark Lofthouse applied considerable pressure), the opportunities we created and the way we communicated. But you can't be happy when you lose."