Yamaha Motor Company Limited 2X5-11637-00-00 Piston

2X5-11637-00-00 is an OEM Yamaha piston designed for two-stroke motorcycle engines, specifically the Yamaha YZ400 from 1979 and similar configurations, and it is offered in the 3rd oversize category with +0.75 mm oversize. The piston is manufactured from aluminum alloy and serves to convert combustion energy into mechanical motion within a two-stroke gasoline engine. It is intended for engine rebuilds or repairs to restore compression and power, and it requires a matched cylinder bore for oversize fitting. This is a genuine Yamaha component sourced from Japan, with limited availability in some listings. Common applications include vintage motocross bikes, restoration projects, and high-performance two-stroke engines where reliable operation and power output are critical. Common replacement part numbers include Yamaha 2X5-11635-00-00, 2X5-11636-00-00, and 2X5-11638-00-00.