A bicycle sprocket includes a plurality of sprocket teeth. The plurality of sprocket teeth includes at least one first tooth and at least one second tooth. The at least one first tooth has a first radial-tooth height. The at least one first tooth has a first chain-engaging axial width which is smaller than a first distance defined between opposed outer link plates of the bicycle chain and which is larger than a second distance defined between opposed inner link plates of the bicycle chain. The first radial-tooth height is greater than the first chain-engaging axial width. The at least one second tooth has a second radial-tooth height. The at least one second tooth has a second chain-engaging axial width. The second radial-tooth height is greater than the second chain-engaging axial width. The first radial-tooth height is greater than the second radial-tooth height.

The present disclosure provides a captive sprocket system for an engine, comprising: a sprocket including a first sprocket gear, a second sprocket gear and a retaining disc having a diameter and a thickness; a cylinder block having a bore with a central opening and a plurality of threaded bosses, the plurality of threaded bosses together forming an axial support surface and a radial location surface, the axial support surface and the radial location surface being sized to receive the retaining disc of the sprocket to support and locate the sprocket; and a plurality of captivation screws configured to be received by the plurality of threaded bosses, each captivation screw having a head with a lower surface which, when the captivation screw is received by a threaded boss, overlies the retaining disc and retains the sprocket in the bore.