O.S. has Updated the .25 SF with this New High-Performance .25 FX. This Engine may be used in Sport and Aerobatic Aircraft. The FX is Designed to Use a Muffler or Tuned Pipe. Comes with a 2-Year Warranty. FEATURES: Remote Needle Attached to the Backplate keeps fingers away from prop Twin Ball Bearing-Supported Crankshaft Schnuerle Porting (Schnuerle scavenging) Advanced Bi-Metallic Liner. This process uses a double layer of plating material, rather than one thicker layer. This helps the metal to bond to the cylinder, and is more durable. Also, the plating process is more consistent, resulting in a more precise fit between piston and sleeve, for better compression, longer life. Side Exhaust One-Piece Crankcase INCLUDES: One Expansion Style Muffler One Set of Instructions, Decal, and Poster One Assembled .25 FX w/Carb SPECS: Displacement: 4.07cc (.2485 cu in) Bore: 18mm (.708") Stroke: 16mm (.630") Horsepower: .84 BHP at 18,000 RPM Weight: 248g (8.8oz) 10.8oz w/muffler Length: 75.6mm (2.98") distance from the backplate to drive washer Width: 30mm(1.18") width of engine neglecting engine mounting flanges 38mm (1.50") distance between centers of the mounting holes Height: 75.5mm (2.97") Crankshaft Thread Size: 1/4-28 Recommended Props: Pattern Flying: 9x5, 9x6 Pattern Flying if a tuned pipe is used: 9.5x5 Sport Flying: 9x5, 9x6, 9.5x5, 10x4, 10x5 Practical RPM Range: 2,500 - 19,000 RPM High Speed Needle: 1.5 - 2 turns out from fully closed Low Speed Needle: 2mm gap between the needle and spray bar at full throttle (looking down the neck of the carb) REQUIRES: Long Glow Plug (O.S. #8 recommended OSMG2691) Fuel with 18% (minimum) lubricant content and 5%-15% Nitromethane (All 5%-15% fuels we carry meet these requirements) ir/jl updated jpg 9/20/05 updt lmm 3/27/09