Kevin Porter, looking more like the perpetual-motion machine of yesteryear that made Washington fans standup and cheer, served notice last night he is back.

The stutter-stepping point guard sitting idle much of this ill-starred Bullet basketball year, was a man on fire in the final quarter as he ignited Washington to a stirring 118-115 triumph over the Cleveland Cavaliers. A good crowd of 11,892 sat in at Capital Centre.

Coach Dick Motta decided just before game time to return home to fight the flu and his assistant, Bernie Bickerstaff, ran the team. Porter took advantage of every one of his 19 minutes, scoring 12 points, registering six assists and hustling from one end of the court to the other.

The Cavaliers, still believing they have a shot at the playoffs despite falling to 26-39, banged home enough jump shots to take the Bullets down to the wire. Washington, going through periods of ups and downs, hit 12 of 16 shots in the third quarter to grab a 96-89 advantage. Elvin Hayes, the night's high scorer with 32 points, tallied 10 in that period.

Three passes from Porter led to Bullet baskets and a 104-96 lead with 9:23 to play. But the Cavs, who take pride in the 22-footer, starting firing and back they came.

Austin Carr (16 points) and Mike Mitchell (22) combined for 14 of Cleveland's 26 fourth-period points to lead the charge. Carr, playing in place of Randy Smith (20 points), faked Porter into the air and rippled an 18-footer from the top of the key to cut the once comfortable Washington lead to 112-111 with 3:03 left.

"Austin was going well so I stayed with him in the final period," said Cleveland Coach Stan Albeck. "Randy carried us the first half and the third period and when Austin went in, he did the job."

Seconds after Carr's basket, Porter breezed past Foots Walker, a replacement assigned to stop the Bullets' speedy guard, for a driving one-hander to make it 114-111. Hayes gave the Bullets a five-point lead on a turn-around jumper off a nice pass inside from Porter.

"When he (Porter) plays well, he plays," remarked Bickerstaff. "In a situation like we're in, struggling for our life, we have to control the ball and Porter took care of the ball tonight."

Negatively, Porter kept the crowd around until the end as he committed two turnovers in the final minute. Both times Cleveland scored.

Dave Robisch sank two free throws after the first Porter mistake. Willie Smith converted a followup bucket after Mitchell's missed three-point attempt, cutting the Cav's deficit to 116-115, with nine seconds left.

Cleveland was forced to foul and Porter, now taking extra good care of the ball, was grabbed by Smith at :007. Porter made both shots to furnish the final three-point margin.

Cleveland went for the equalizer but Mitchell's 25-foot bomb banged off the side of the rim.

Porter first came during the second period to score six points. He said he was "glad the team won but didn't feel my floor game was that good.

"It doesn't take long for me to get in playing shape," said Porter, who played well at Los Angeles in the Bullets' final game of their recent seven-game road trip. "I haven't played much and it takes time to get in the flow of the game. We wanted to get in a running game and get the ball down low to our big people. We like to do that to a young team like Cleveland. Not many people can match Elvin and Wes (Unseld) down low."

Hayes enjoyed a good start, pouring in 12 points over Mitchell in the first quarter. Greg Ballard, starting again in place of injured Bobby Dandridge, scored 10 of his 26 in the period to help Washington creep out to a 32-26 lead.

But the Cavs, who had split four previous games with the Bullets, got good scoring from Smith and Robisch in the second quarter to cut the deficit at intermission to 60-58.

"We missed a few layups in the first half and a few balls bounced the wrong way," Albeck said. "But we've been in every game this year. This is the 19th game we've lost by four points or less."

Cleveland did all it could to avert the loss in the third quarter, jumping ahead by as many as five points. But Washington, outrebounded by the scuffling visitors (45-43), began to pound the backboards in the period and converted a few layups. Jim Cleamons, on a five-of-six shooting night, threw in three baskets in the final minutes of the period to fire the Bullets into a 96-89 lead over his old team going into the final quarter.

Newly acquired designated shooter John (Supe) Williamson didn't exactly endear himself to the fans in his first home appearance in a Bullet uniform. He missed his only attempt in the first half and was tagged with three personals. Williamson did hit two baskets and a pair of free throws for six points in his 11-minute stint.

"I guess John wasn't too happy with his time but I have to go with the way I feel," said Bickerstaff. "The team played hard tonight. In fact, they played hard the entire seven-game road trip (Washington won only two of the seven games)."

Washington, now 26-34, plays 13 of its final 22 games at Capital Centre. The Bullets entertain the San Antonio Spurs and league scoring king, George Gervin tonight at 8.