he first day of Metro's grand experiment to stop buses at outlying subway stations and force thousands of commuters to travel by trian came off with a minumum of trouble yesterday but with enough incidents to show it needs fine-tuning.

"It went surprisingly wellk," Metro General Manager Theodore Lutz said as he watched buses cart off home bound commuters pouring out of the Rosslyn Metro station. "Thank God it didn't rain during rush hour."

It just missed. A brief lightning-punctuated gully-washer dumped more than 1 inch of rain in 45 minutes after 3 p.m. and knocked out the electricity for the Rosslyn station and its escalator - the world's second longest.

Metro officials had visions of hundreds of commuters unloading from smooth-running trains (which have back-up electricity) but then having to hike up the 210-ft., 8-inch-long non-operating escalator. Pepco got the power back on in about 30 minutes, before the evening crush.

There was one major train break down during the morning rush hour and two in the evening. Considering the trouble Metro has had running reliable trains since it expanded its subway service July 1, that was remarkable.

A total of 210 bus routes were climinated or changed yesterday to feed commuters into the subway and thus save Metro money by reducing bus costs and increasing subway revenues.

Metro had predicted that about 30,000 commuters would be affected. Although there was confusion and misunderstanding on the part of many bus patrons, many more seemed to know what they were doing.

Major bus terminals were created at the Rosslyn. Stadium-Armory, Potomac Avenue and Federal Center SW Metro stations. Most of those interchange arrangements worked well. One, at Potomac Avenue, presented the kind of carefully planned snalu that only Metro with its multiplicity of political players could duplicate.

The Potomac Avenue Station, at 14th Street and Pennsylvania and Potomac Avenues SE. was built with three immediately adjacent concrete bus bays on 14th Street SE.

But Maryland and District of Columbia residents forced off their buses at that station had to cross Potomac Avenue in the morning, and Potomac Avenue and six lanes of rush-hour traffic on Pennsylvania Avenue in the evening. The bus bays were filled with parked cars.

The other major problems yesterday were that some people did not understand the complicated fare-transfer procedure and others do not like trains.

For example, most bus routes that used to cross Key Bridge were terminated at Rosslyn yesterday. A new route, to connect Rosslyn with Georgetown was inaugurated. Hundreds of commuters got off their buses at the Rosslyn station and instead of taking the train transferred to the new Key Bridge route, the M6.

One woman told a reporter that she was not going to ride the Metro because "if the good Lord meant us to be underground, he would have made us moles."

Allyn Amato, a State Department employee who lives in Arlington Towers and waited at Rosslyn to board the M6. called the bus turnback plan "ridiculous." "You can see for yourself," he said, "that the buses that go downtown are packed." He was right.

The trains were packed, too. Most people - Metro thinks a majorityal-ready had purchased the magnetically encoded Farecard they needed to board and leave the train stations. Farecard problems were enormous the first day that system was used, July 1, but yesterday they were minimal.

In the inter-ening month, more Farecard equipment has been installed at many Metro stations, and thousands of subway riders have learned how to use the equipment. They also have learned that a week's worth of rides or more can be purchased at one time, thus shortening the lines at the Farecard vending machines.

Some Metro users learned for the first time yesterday that they could not transfer from the bus to the train and that they would have to pay a second fare to get to work.

At the Stadium-Armory station, for example, a few angry riders insisted on exchanging their bus transfers for Metro Farecards. Station attendants were firm.

"I paid 50 cents for this and you mean I can't get anything for this?" Mary Williams demanded of Metro staffer Cleveland R. Amos.

"When you go rail, you have to pay rail fare," he said.

Riders can transfer from the train to the bus, and many did so in the evening without difficulty. Transfers must be obtained from automatic vending machines at the station where the rider enters the Metro system, however.

Another complaint came from those who once rode express buses from where they lived to where they worked and yesterday discovered that they could no longer do that.

Judith Zilczer, a historian at the Hirshhorn Museum at Independence Avenue and 8th Street SW was in that category. Her bus used to take her from Glebe Road and Lee Highway to the front of the Hirshhorn. Yesterday it stopped at Federal Triangle, where she had to change to the train (and pay extra fare) or walk eight blocks. "It stinks," she said. "The way the system works today, I'm more inclined to use my car." The bus-to-train transfer costs her 20 minutes in total travel time, she said.

No day would be complete on the Metro without one sticking door. When Metro's doors stick, as they do sometimes where there is a heavy load of people, the trains will not go.

That happened during the evening rush hour at the Federal Triangle Station. As the jam-packed train refused to go. Ginger Harding of Oxon Hill told a friend. "I'm getting claustrophobic. I'm going to start screaming." She didn't, but put her head in her hands instead.

"I'll hitch-hike before I'll do this again," she said. She called it her first and last subway ride. She previously had taken a bus door-to-door from her home to her job downtown, but the bus was curtailed.

Her train was one of two with door problems that slowed the evening rush. The morning rush was run with one decay on the older Red Line when the brakes locked on an "overloaded" car.

For the first time since July 1, Metro had most of its equipment running. All trains on the Blue Line had six cars and 12 trains ran during both rush hours. If all 12 run well, Metro can maintain 6-to seven-minute intervals with that much equipment.

That leaves the Potomac Avenue Station situation. There is disagreement between Metro and D.C. as to whether D.C. approved the bus bays on 14th Street. The Metro plan was to stop buses there, then turn them around on residential streets. Neighborhood citizens protested at public hearings and a compromise was sought.

Most of the bus routes stopped at Potomac Avenue are from Prince George's County. D.C. proposed that the buses go to the Stadium Metro station, which would require the buses to back-track. Prince George's objected to the back-tracking because it would cost the county more in subsidies since mileage is a factor in the subsidy formula.

The solution was to use Pennsylvania Avenue as the bus stop. Yesterday evening, as commuters poured across the avenue, waiting outbound buses blocked the driveway of the Capitol Hill Texaco at 1401 Pennsylvania Avenue SE.

"I'll give 'em a couple of days to work this out, but I've got to do something to protect my business during rush hour," station manager Frank Dickens said.