The purse of the 1986 Jersey Derby will be increased to $2 million and the bonus for winning four specified races enhanced to $5 million, Robert Brennan, Garden State Park's chairman of the board, said yesterday.

The announcement came four weeks after owner Dennis Diaz's decision to run Kentucky Derby winner Spend a Buck in the $1 million Jersey Derby in lieu of Pimlico's $350,000 Preakness Stakes, the second leg of racing's Triple Crown. The Jersey Derby victory gave Spend a Buck a record $2.6 million payday, $2 million coming as a bonus for also having won the Kentucky Derby, Cherry Hill Mile and Garden State Stakes.

Concerned that more lucrative purses would lure horses from the Triple Crown races, officials of Pimlico, Churchill Downs (Kentucky Derby) and the New York Racing Association (Belmont Stakes) met after the Kentucky Derby to discuss bonuses for winning their races.

Pimlico General Manager Chick Lang Sr., informed of Brennan's announcement yesterday afternoon, said enhancement of Triple Crown purses is imminent.

"Something will be done sometime before next year's Triple Crown races," Lang said. "We will have discussions in the near future. We'll just have to sit back and analyze what has been done (by Brennan).

"As far as ourselves, we have to determine where we've been, where we are and where we're going. But I don't want to overreact."

Meanwhile, trainer Cam Gambolati said Spend a Buck likely will run next in the $300,000 Haskell Memorial Handicap June 27 at Monmouth Park.

With assistance from a Laurel Race Course kitchen employe, jockey Dimitrios Dimitropoulos has produced three victories in six mounts since he began riding in Maryland last week.

Dimitropoulos, an 18-year-old native of Athens, has used cook Angelos Dalmanieras as an interpreter when discussing tactics with trainers.

Dimitropoulos, Martin Ramirez of Mexico and Gavin Van Zyl of South Africa are jockeys participating in their first Bowie meeting.

Ramirez, a 20-year-old apprentice, has replaced Sean Jones as the No. 1 jockey for trainers Ron Alfano and Dick Dutrow. After four winless mounts Monday, Ramirez won yesterday astride Chimney Soot ($18.60), Mr. Bushrod ($11) and Courthouse Steps ($7.20).

E.T. McLean has been named racing secretary and handicapper for Timonium's 10-day meeting that begins Aug. 24. McLean, 46, replaces Tommy Baker; he chose Billy Passmore Jr. as his assistant.

Quest Man, a 5-year-old horse beaten by 40 lengths in his only previous 1985 start, rallied to victory in yesterday's ninth race at Bowie to key a triple payoff of $18,013.50.

Quest Man (30 to 1) won his second race in 24 starts for trainer James Russell. Bowie's record triple payoff is $68,881.50, set Oct. 4, 1974.