…..Yamaha Apex (150 FI) models feature a sleeveless plated cylinder design, where the previous carbureted RX-1 engine had plated cylinders with sleeves. The change is said to improve heat displacement on the higher-powered fuel-injection engine. In addition, the FI version has an oil pressure sensor. The pistons and rings (and connecting rods), however, are the same as the 2005 carbed models.
