SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 4) SUN HYDRAULICS CORPORATION - ------------------------------------------------------------------------------- (Name of Issuer) COMMON STOCK, PAR VALUE $0.001 PER SHARE - ------------------------------------------------------------------------------- (Title of Class of Securities) 866942 10 5 - ------------------------------------------------------------------------------- (CUSIP Number) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [ ] Rule 13d-1(b) [ ] Rule 13d-1(c) [X] Rule 13d-1(d) * The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act, but shall be subject to all other provisions of the Act (however, see the Notes). CUSIP NO. 866942 10 5 13G Page 2 of 11 - ------------------------------------------------------------------------------- 1) Names of Reporting Persons/ I.R.S. Identification Nos. of Above Persons (Entities Only) Robert E. Koski - ------------------------------------------------------------------------------- 2) Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] - ------------------------------------------------------------------------------- 3) SEC Use Only - ------------------------------------------------------------------------------- 4) Citizenship or Place of Organization U.S. - ------------------------------------------------------------------------------- Number of (5) Sole Voting Power Shares Beneficially 117,162 Owned by Each (6) Shared Voting Power Reporting Person 2,501,758 With (7) Sole Dispositive Power 117,162 (8) Shared Dispositive Power 2,501,758 - ------------------------------------------------------------------------------- 9) Aggregate Amount Beneficially Owned by Each Reporting Person 2,618,920 - ------------------------------------------------------------------------------- 10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares [ ] (See Instructions) - ------------------------------------------------------------------------------- 11) Percent of Class Represented by Amount in Row (9) 41.02% - ------------------------------------------------------------------------------ 12) Type of Reporting Person (See Instructions) IN - ------------------------------------------------------------------------------- CUSIP NO. 866942 10 5 13G Page 3 of 11 - ------------------------------------------------------------------------------- 1) Names of Reporting Persons/ I.R.S. Identification Nos. of Above Persons (Entities Only) Beverly Koski - ------------------------------------------------------------------------------- 2) Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] - ------------------------------------------------------------------------------- 3) SEC Use Only - ------------------------------------------------------------------------------- 4) Citizenship or Place of Organization U.S. - ------------------------------------------------------------------------------- Number of (5) Sole Voting Power Shares Beneficially 141,215 Owned by Each (6) Shared Voting Power Reporting Person 2,477,705 With (7) Sole Dispositive Power 141,215 (8) Shared Dispositive Power 2,477,705 - ------------------------------------------------------------------------------- 9) Aggregate Amount Beneficially Owned by Each Reporting Person 2,618,920 - ------------------------------------------------------------------------------- 10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares [ ] (See Instructions) - ------------------------------------------------------------------------------- 11) Percent of Class Represented by Amount in Row (9) 41.02% - ------------------------------------------------------------------------------- 12) Type of Reporting Person (See Instructions) IN - ------------------------------------------------------------------------------- CUSIP NO. 866942 10 5 13G Page 4 of 11 - ------------------------------------------------------------------------------- 1) Names of Reporting Persons/ I.R.S. Identification Nos. of Above Persons (Entities Only) Christine L. Koski - ------------------------------------------------------------------------------- 2) Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] - ------------------------------------------------------------------------------- 3) SEC Use Only - ------------------------------------------------------------------------------- 4) Citizenship or Place of Organization U.S. - ------------------------------------------------------------------------------- Number of (5) Sole Voting Power Shares Beneficially 64,295 Owned by Each (6) Shared Voting Power Reporting Person 2,333,543 With (7) Sole Dispositive Power 64,295 (8) Shared Dispositive Power 2,333,543 - ------------------------------------------------------------------------------- 9) Aggregate Amount Beneficially Owned by Each Reporting Person 2,397,838 - ------------------------------------------------------------------------------- 10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares [ ] (See Instructions) - ------------------------------------------------------------------------------- 11) Percent of Class Represented by Amount in Row (9) 37.55% - ------------------------------------------------------------------------------- 12) Type of Reporting Person (See Instructions) IN - ------------------------------------------------------------------------------- CUSIP NO. 866942 10 5 13G Page 5 of 11 - ------------------------------------------------------------------------------- 1) Names of Reporting Persons/ I.R.S. Identification Nos. of Above Persons (Entities Only) Robert C. Koski - ------------------------------------------------------------------------------- 2) Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] - ------------------------------------------------------------------------------- 3) SEC Use Only - ------------------------------------------------------------------------------- 4) Citizenship or Place of Organization U.S. - ------------------------------------------------------------------------------- Number of (5) Sole Voting Power Shares Beneficially 15,000 Owned by Each (6) Shared Voting Power Reporting Person 2,360,543 With (7) Sole Dispositive Power 15,000 (8) Shared Dispositive Power 2,360,543 - ------------------------------------------------------------------------------- 9) Aggregate Amount Beneficially Owned by Each Reporting Person 2,375,543 - ------------------------------------------------------------------------------- 10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares [ ] (See Instructions) - ------------------------------------------------------------------------------- 11) Percent of Class Represented by Amount in Row (9) 37.21% - ------------------------------------------------------------------------------- 12) Type of Reporting Person (See Instructions) IN - ------------------------------------------------------------------------------- CUSIP NO. 866942 10 5 13G Page 6 of 11 - ------------------------------------------------------------------------------- 1) Names of Reporting Persons/ I.R.S. Identification Nos. of Above Persons (Entities Only) Thomas L. Koski - ------------------------------------------------------------------------------- 2) Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] - ------------------------------------------------------------------------------- 3) SEC Use Only - ------------------------------------------------------------------------------- 4) Citizenship or Place of Organization U.S. - ------------------------------------------------------------------------------- Number of (5) Sole Voting Power Shares Beneficially 0 Owned by Each (6) Shared Voting Power Reporting Person 2,333,543 With (7) Sole Dispositive Power 0 (8) Shared Dispositive Power 2,333,543 - ------------------------------------------------------------------------------- 9) Aggregate Amount Beneficially Owned by Each Reporting Person 2,333,543 - ------------------------------------------------------------------------------- 10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares [ ] (See Instructions) - ------------------------------------------------------------------------------- 11) Percent of Class Represented by Amount in Row (9) 36.55% - ------------------------------------------------------------------------------- 12) Type of Reporting Person (See Instructions) IN - ------------------------------------------------------------------------------- CUSIP NO. 866942 10 5 13G Page 7 of 11 - ------------------------------------------------------------------------------- 1) Names of Reporting Persons/ I.R.S. Identification Nos. of Above Persons (Entities Only) Koski Family Limited Partnership EIN: 75-2707549 - ------------------------------------------------------------------------------- 2) Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] - ------------------------------------------------------------------------------- 3) SEC Use Only - ------------------------------------------------------------------------------- 4) Citizenship or Place of Organization U.S. - ------------------------------------------------------------------------------- Number of (5) Sole Voting Power Shares Beneficially 0 Owned by Each (6) Shared Voting Power Reporting Person 2,333,543 With (7) Sole Dispositive Power 0 (8) Shared Dispositive Power 2,333,543 - ------------------------------------------------------------------------------- 9) Aggregate Amount Beneficially Owned by Each Reporting Person 2,333,543 - ------------------------------------------------------------------------------- 10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares [ ] (See Instructions) - ------------------------------------------------------------------------------- 11) Percent of Class Represented by Amount in Row (9) 36.55% ------------------------------------------------------------------------------- 12) Type of Reporting Person (See Instructions) PN - ------------------------------------------------------------------------------- CUSIP NO. 866942 10 5 13G Page 8 of 11 - ------------------------------------------------------------------------------- SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13d-1(b) OR 13d-2(b) Item 1(a). Name of Issuer: SUN HYDRAULICS CORPORATION Item 1(b). Address of Issuer's Principal Executive Offices: 1500 West University Parkway Sarasota, FL 34243 Item 2(a). Name of Person Filing: Robert E. Koski Beverly Koski Christine L. Koski Robert C. Koski Thomas L. Koski Koski Family Limited Partnership Item 2(b). Address of Principal Business Office or, if none, Residence: 1500 West University Parkway Sarasota, FL 34243 Item 2(c). Citizenship: U.S. Item 2(d). Title of Class of Securities: Common Stock, Par Value $0.001 per share Item 2(e). CUSIP Number: 866942 10 5 Item 3(a). If this statement is filed pursuant to Rule 13d-1(b), or 13d-2(b), check whether the filing person is a: (a) [ ] Broker or Dealer registered under Section 15 of the Act; (b) [ ] Bank as defined in Section 3(a)(6) of the Act; (c) [ ] Insurance Company as defined in Section 3(a)(19) of the Act; (d) [ ] Investment Company registered under Section 8 of the Investment Company Act; (e) [ ] Investment Adviser registered under Section 203 of the Investment Advisers Act of 1940; CUSIP NO. 866942 10 5 13G Page 9 of 11 - ------------------------------------------------------------------------------- (f) [ ] Employee Benefit Plan, Pension Fund which is subject to the provisions of the Employee Retirement Income Security Act of 1974, or Endowment Fund; see Rule 13d-1(b)(1)(ii)(F); (g) [ ] Parent Holding Company, in accordance with Rule 13d-1(b)(ii)(G) (Note: See Item 7); (h) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(H) Item 4. Ownership: If the percent of the class owned, as of December 31, of the year covered by the statement, or as of the last day of any month described in Rule 13d-1(b)(2), if applicable, exceeds five percent, provide the following information as of that date and identify those shares which there is a right to acquire. (a) Amount Beneficially Owned: See Response to Item 9 on cover pages. (b) Percent of Class: See Response to Item 9 on cover pages. (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote: See Response to Item 5 on cover pages. (ii) shared power to vote or to direct the vote: See Response to Item 6 on cover pages. (iii) sole power to dispose or to direct the disposition of: See Response to Item 7 on cover pages. (iv) shared power to dispose or to direct the disposition of: See Response to Item 8 on cover pages. Item 5. Ownership of Five Percent or Less of a Class: Not applicable Item 6. Ownership of More than Five Percent on Behalf of Another Person: Not applicable Item 7: Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company: Not applicable Item 8: Identification and Classification of Members of the Group: Not applicable Item 9: Notice of Dissolution of Group: Not applicable Item 10: Certification: Not applicable CUSIP NO. 866942 10 5 13G Page 10 of 11 - ------------------------------------------------------------------------------- SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. January 31, 2000 /s/ Robert E. Koski ---------------------------------- ROBERT E. KOSKI /s/ Beverly Koski ---------------------------------- BEVERLY KOSKI /s/ Christine L. Koski ---------------------------------- CHRISTINE L. KOSKI /s/ Robert C. Koski ---------------------------------- ROBERT C. KOSKI /s/ Thomas L. Koski ---------------------------------- THOMAS L. KOSKI KOSKI FAMILY LIMITED PARTNERSHIP By: /s/ Christine L. Koski ---------------------------------- Christine L. Koski, Managing Partner CUSIP NO. 866942 10 5 13G Page 11 of 11 - ------------------------------------------------------------------------------- EXHIBIT A RULE 13d-1(k) AGREEMENT The undersigned agree and consent to the joint filing on their behalf of this Schedule 13G in connection with their beneficial ownership of the common stock of Sun Hydraulics Corporation at December 31, 1999. /s/ Robert E. Koski ---------------------------------- ROBERT E. KOSKI /s/ Beverly Koski ---------------------------------- BEVERLY KOSKI /s/ Christine L. Koski ---------------------------------- CHRISTINE L. KOSKI /s/ Robert C. Koski ---------------------------------- ROBERT C. KOSKI /s/ Thomas L. Koski ---------------------------------- THOMAS L. KOSKI KOSKI FAMILY LIMITED PARTNERSHIP By: /s/ Christine L. Koski ------------------------------- Christine L. Koski, Managing Partner