¶1The adjudication below of delinquency for grand theft of a dirt bike is reduced to petit theft because the evidence was insufficient to establish that the value of the bike at the time of the theft was more than *1279the $300 statutory amount. See § 812.014(2)(c)l, Fla. Stat. (2003). Specifically, evidence simply that the bike had been purchased seven months before for $3000, without any expert or other testimony concerning the extent of the dimin-ishment in value caused by both its use and the fact that, as the evidence showed, significant damage was sustained by the bike during that period, was legally insufficient. See Negron v. State, 306 So.2d 104 (Fla.1974). A conviction on the more serious charge cannot be based, as it apparently was here, upon what must be the purely speculative conclusion that the bike “could not” have depreciated or its value diminished that much. See J.O. v. State, 552 So.2d 1167 (Fla. 3d DCA 1989).
¶2Affirmed as modified.