From inside (document excerpt):
Parts MANUAL ZERO TURN TRACTOR Model Numbers ZT 4200 w/42 ” Mower Deck ZT 5000 w/50 ” Mower Deck IMPORTANT: READ SAFETY RULES AND INSTRUCTIONS CAREFULLY Warning: This unit is equipped with an internal combustion engine and should not be used on or near any unimproved forestcovered, brush-covered or grass-covered land unless the engine’s exhaust system is equipped with a spark arrester meeting applicable local or state laws (if any). If a spark arrester is used, it should be maintained in effective working order by the operator.
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In the State of California the above is required by law (Section 4442 of the California Public Resources Code). Other states may have similar laws. Federal laws apply on federal lands. A spark arrester for the muffler is available through your nearest engine authorized service dealer or contact the service department, P.O. Box 361131 Cleveland, Ohio 44136-0019. MTD LLC, P.O. BOX 361131 CLEVELAND, OHIO 44136-0019 PRINTED IN U.S.A. FORM NO. 769-02842 (2/07) FRAME: MODELS ZT4200 AND ZT5000 REF. PART NO. NUMBER 1 603-04303C.
Wikipedia’s page for MTD Products
Company Web Site: www.mtdproducts.com
Very helpful info