CONSUMERS in the market for lawn mowers have a choice: They can buy a mower this year and pay less for it or they can buy a safer mower in spring 1983 for $20 to $75 more.

The Consumer Product Safety Commission has amended its standards for walk-behind power lawn mowers made after June 30, 1982. But since most of the lawn mowers in stores now and in the summer were made before that date, the current stock will be cheaper but will not have the new safety features.

According to Carl Blechschmidt, program manager of power equipment for CPSC, the new standards provide that "once an operator lets go of the handle, the blade should stop within three seconds. The new mechanism, the blade break, stops the blade but leaves the engine running."

The amendment to the new standards, according to the CPSC final briefing, says that "a lawn mower with only manual starting controls, which meets the requirements of the present standard except that the blade control system stops the blade by stopping the engine, shall be allowed if:

"(1) the engine-starting controls for the lawn mower are located within 24 inches of the top of the mower's handle, or . . .

"(2) the mower has a protective foot shield which extends 360 degrees around the mower housing."

In other words, says Blechschmidt, "the new standards and amendment allow the manufacturer to make a manual-starting mower whose engine will stop to meet the blade stopping time of three seconds. The manufacturer can do this by either of the following: 1) building the mower's starting controls no more than 24 inches from the top of the handle, or 2) if you have to walk around the lawn mower's motor to turn it off, the manufacturer must include a foot shield 360 degrees around the mower."

Bleschschmidt says that the new regulations will not affect the price or design of mowers during the '82 garden season.

Jerry Brace, garden equipment buyer for Hechinger's, adds: "Lawn mower manufacturers begin working on new models in September, so it'll be next year before we see the increase in price." The electric restart models will probably be the most expensive, with gas models not far behind. Manual restart models will see the least increase in price.

More than 77,000 injuries per year prompted the new regulations, according to Blechschmidt. Safety

With or without the new safety feature, precautions should always be taken when using a lawn mower. "As any power tool, lawn mowers should be treated with respect," said David Robinson, co-owner of Lane's Mower Service. "Maybe it's because most people have grown up with them, but people don't take care the way they should."

Never clean or tamper with a lawn mower while it's still on, warned Robinson. "That includes removing clogged grass, pulling out twigs and taking off any bags." Never put your feet and hands beneath a running mower.

"It's always a good idea to check the lawn before mowing for glass, rocks, dog bones, beer cans, etc.," added Robinson. "Don't try to eyeball it as you go along. I know a guy who was struck with a stray piece of glass. It entered and exited his calf with the speed of a 22-calibre bullet."

Robert Bradley, owner of Bradley's Lawn Mower Shop in Falls Church, agreed. He adds that in addition to hurting someone, these stray objects can damage the mower itself. A bent crank shaft is expensive to repair.

John Klapac, who runs lawn mower repair workshops (see below), said that you should never mow after a rain or while the lawn is wet. "Grass is harder to mow when it's wet and it's too easy for a foot to slip beneath a mower with wet grass."

He also recommends that children be supervised while mowing the lawn, "although, I have to admit that most of the injuries I've seen are to people over age 21." Preventive Maintenance

Robinson said that the average homeowner uses either a four or two cycle motor. A four cycle engine has one place to put the oil and another for the gas. With a two cycle engine the gas and oil are mixed together before they're put into the engine.

With a four-cycle engine, Robinson advised changing the oil "at least once a season, depending on the machine and how much it's used. Check the lawn mower manual; most recommend changing the oil every 25 hours or 1 1/2 times per season."

Both types of machines need to have their air filters cleaned regularly, two or three times a season, according to Robinson.

The blade should be sharpened several times a year, again, depending on use. "Believe it or not," says Robinson, "cutting grass will dull a blade." The blades can be filed with a metal file. The blades should also be balanced, distributing their weight evenly throughout the blade. "When a blade is not balanced, it will vibrate while it's on the mower, causing the nuts and bolts to come loose." Klapac suggests hanging the blade on a nail drilled into the wall to see if it's balanced.

The spark plug should also be changed once or twice a year. They cost about $2 and are located in back of the mower.

Don't leave your mower to the weather. Store it in the garage. If you don't have a garage and must leave it outside, cover it with a drop cloth, an old tablecloth or plastic cover. "Moisture will build up in the working parts of the lawn mower's engine when it's outside," says Klapac. "Corrosion will set it." Not surprising, Klapac said, since he believes many lawn mowers are cheaply built. "They're considered throw away items by some manufacturers. After two years, the consumer usually has to buy a new one."

Never hose down your mower to clean it. "Water will get into the motor and ruin the machinery," says Bradley. "Wipe with a damp rag instead after each use, always waiting for the machine to cool down first."

To remove dead grass from the bottom of the mower, Robinson suggests prying it off with a putty knife.

John Klapac says you shouldn't try to cut grass that's grown too high, since it will clog up the machine. "Use a sickle barb mower or a reel mower," advised Klapac. "But be extremely careful with the former. The sickle barb mower's blades are completely exposed.

"When storing your mower for the winter," adds Klapac, "put oil or an oil-product called 'Staple' in with the gas, to keep the inner passages of the carburetor lubricated. This will prevent corrosion in the carburetor."

Most lawn mower repair shops will advise you to stop here before doing any further repairs. And if you're not particularly handy or ambitious you may agree. A tune-up from area repair shops costs about $35 for the average gas rotary mower. They usually include some of the above such as oil changes, sharpening and balancing the blades, changing the spark plug, but they will also clean and adjust your carburetor, as well as change the points in your condenser. Some models no longer have points. A tune-up is recommended every other year.

However, if you want to save money and enjoy tinkering, you might be able to handle a few slightly more advanced repairs (changing cables, lubricating wheels). Former garage operator, repairman and currently apiary owner John Klapac will present a gas lawn mower repair workshop April 17, 9 a.m. to 5 p.m. at Berwyn Heights Elementary School, 6200 Pontiac St., Berwyn Heights. Sponsored by the Maryland National Capital Park and Planning Commission and the Berwyn Heights Recreation Council, the workshop will include basic mechanics, preventive maintenance, tune-ups and repairs. Deadline for registration is April 7. Fee: $20. Call 445-4500 to register. Klapac claims that with only a $12 investment in tools you can take care of most common mower repairs. The Mower Market

Lane's Garden Center (unrelated to Lane's Mower Service) carries push- and self-propelled-model mowers by Lawn Boy, John Deere, Toro and Snapper, starting at $250. Manager and part-owner William Obear says they also carry "riding" mowers by John Deere and Snapper, beginning at $1,000. The riding mowers, explains Obear, have the engine in the back. Lane's sells tractor mowers for $2,800 to $4,000. These have engines in front. Sear's has rotary mowers for $150; rear-bag mowers for $190; and power-propelled rear-baggers for $270. They also have lawn tractors for $880. Hechinger's is carrying push mowers, $54 to $79.95; electric mowers, $129.95 to $179.95; and power mowers, $129.95 to $399. Hechinger's also has an eight-horsepower riding tractor with a 30-inch mower deck for $889.95, and a deluxe 16-horsepower model with a 44-inch mower deck for $1,999.95.