Zenoah G290RC 29cc 4 Bolt Engine with Clutch and Carb The Brand-New 2010 Zenoah G290RC engine is a 28.5cc (36mm bore, 28mm stroke) performance machine. Zenoah took their powerful, reliable G260RC engine and made it even better. Major changes include a 4-bolt cylinder design for improved sealing and reduced gasket blowout (an improvement from the 2-bolt cylinder design of the G260RC); a stronger and lighter crankcase; an additional crankshaft bearing; redesigned cylinder fins for better cooling; larger ports; the high-performance WT-990 carburetor as standard equipment; a metal-impregnated insulator gasket for a better seal; and modified cylinder hardware to better resist vibration. This engine offers serious performance. It features a 4 transfer port 36mm cylinder, Walbro WT-990 carburetor (15.88mm bore, 12.7mm venturi, independent high and low jets), lighter flywheel, "hemi"-style combustion chamber, and full-circle crankshaft. Includes 54mm inner clutch assembly preinstalled. Includes installation instructions.