This is the O.S. Engines GT15HZ Gasoline Powered Helicopter Engine without Muffler. FEATURES: Ideal for sport, 3D and scale pilots Fits most .90 size helis with minor modifications O.S. Walbro developed pumper carburetor for consistent performance regardless of attitude, altitude, or fuel level IG-05 ignition module designed specifically for helis and is compatible with a wide range of battery chemistries including NiCd NiMH, LiPo and Life packs Two year limited warranty through Hobby Services beginning at date of purchase INCLUDES: O.S. Engines GT15HZ Engine with CM-6 Spark Plug, IG-05 Ignition Module, two Servo Throttle Arms, and Instruction Manual REQUIRES: Gasoline: Regular unleaded 2-Stroke Engine Oil Ignition Battery: 4.8-8.4V NiCd, NiMH, 6.6V LiFe or 7.4V LiPo pack, at least 1500mAh Muffler: Depending on application SPECS: Displacement: 0.912 cu in (14.95cc) Bore: 1.091" (27.7mm) Stroke: 0.976" (24.8mm) Practical RPM: 2,000 - 16,000 Output: 2.76hp @ 14,000 RPM Weight: Engine, 26.4oz (748g) IG-05 Ignition Module, 3.2oz (92g) Power Boost Pipe, 7oz (198g) E-4051 Muffler5oz (144g) Carburetor Adjustments; If engine responds sluggishly to increased RPM, turn slow needle right 5° and advance throttle stick gradually If engine hesitates before picking up speed, turn slow needle left 10° to richen mixture Gasoline/Oil Mix: 25:1 Distance/Mounting Hole Centers Same Side: 1.02" (26mm) Distance/Mounting Hole Centers Opposite Side: 2.1" (53mm) Height/Mounting Tab Bottom to top of Cylinder Head: 3.5" (88mm) Height/Crankcase Bottom to top of Cylinder Head: 4.3" (109mm) Width at Mounting Tabs: 2.4" (61mm) Width of Crankcase below Mounting Tabs: 1.7" (42.5mm) Distance between Exhaust Mounting Hole Centers: 1.6" (42mm) Length from Center of Engine to Front Bearing: 2" (52mm) Length from Backplate to Front Bearing: 3.14" (80mm) Length from Center of Engine to end of Crankshaft 3.5" (88mm) Length from Backplate to end of Crankshaft: 4.75" (121mm) jxs 01/16/13 ir/jxs