Sophisticated gamblers disdain systems. They know that winning money on horse races or other sports events requires thorough analysis, not the application of a simple rule or two. The "sure-fire" systems advertised in all the gambling publications are devised by charlatans and used by dimwits.

So I am slightly embarrassed toi admit that I have discovered two sure-fire gambling systems. One is for horses and one is for basketball; both work only in special situations that arise during the springtime; both have been dazzlingly successful over the years.

And both are so simple that I never can bring myself to bet on them blindly.

My ingrained skepticism about systems has cost me a small fortune. When State Dinner won the Metropolitan Handicp at Belmont Park on Monday and paid $61.40, I probably frittered away my last chance of the season to cash in on the Springtime Shipper System. But the Road Team Pro Basketball Playoff System is still operative, and (regrettably) it calls for a serious wager on Seattle plus 4 points against the Bullets tonight.

The Springtime Shipper System has one rule: Bet any horse that is racing in New York whose previous race was run in California.

In rencent years, increasing numbers of trainers have left Aqueduct and Belmont during the winter months and taken their stables to the West Coast. They usually return in April or May, and when they do their horses win with astonishing frequency.

This phenomenon is explained partly - but not entirely - by the fact that racing in the East is less competitive than in the West. Many horses, however, run poorly in New York in the fall and poorly in California during the winter, then return to New York in the spring and win. There may be something about the west-to-east trip that makes horses improve.

Implausible as this might sound, the success of California shippers in New York is an established fact, and this year I was tempted to make an automatic $100 bet on every horse who qualified under the system. I finally decided that this was too simplistic an approach, beneath the dignity of the World's Greatest Handicapper, but that decision cost me dearly.

Some 34 California shippers have raced in New York since the first of April. Eleven of them have won, returning an average payoff of $17.80. My $100 bets would have produced a profit of $6,420. Next year, I'll have more faith.

I do have faith in the Road Team Pro Basketball Playoff System, whose one rule is: Bet the visiting team in the fifth, sixth and seventh games of any NBA playoff series.

This system is firmly rooted in logic. During pro basketball's interminable regular season, home teams have a tremendous advantage, for many well-known reasons: They are motivated to do well before the home crowd; they may be less travel-weary; the referees may treat them kindly. And point spreads fully reflect the home-court advantage.

During the playoffs, however, the factors favoring the home team disappear. Visiting clubs are highly motivated; they won't be suffering from the effects of a long road trip; they aren't likely to be victimized by partisan officiating. After each team has had a couple of games in which to familiarize itself with its opponent's home court, the home-court advantage ceases to be a significant factor by Games 5, 6 and 7.

The players acknowledge this. Whenever one is asked, before a critical game, what the effect of the 20,000 screaming fans is likely to be, he invariably will answer: None at all. Yet the point spreads are made as if a significatn home-court advantage still exists.

Washington and San Antonio were as evenly matched as two teams can be in their conference playoff series. Yet in the sixth game of that series, the Spurs were favored by 3 1/2 at home (Washington won by 8). In the seventh game, Washington was favored by 5 1/2, but won by only 2 points and failed to cover the spread.

During all the NBA playoff series this season, the Road Team Pro Basketball Playoff System has produced 10 winners, three losers and one tie. It has had similar success in previous seasons.

That record suggests that the Sonics are a sound bet to cover the spread against the Bullets tonight. When you use a system, you're not allowed to let sentiment get in the way.