This is the Pro .39H Ringed Two Stroke Helicopter Engine from Thunder Tiger.

FEATURES: Fits all popular 30 size helicopters with gear ratios between 9.1:1
            to 9.8:1
          Developes peak horsepower at 16,000-18,000RPM
          Crankshaft supported by two ball bearings
          Lightened hypereutectic machined Al-Si ringed piston
          Two-needle air-bleed carburetor
          XC2 (extreme composite) cylinder liner coating with a criss-cross
            pattern etched on the sleeve wall
          Rear reinforced resin cage ball bearing support
          Three year limited warranty through Hobby Services beginning at date
            of purchase

INCLUDES: Pro .39H Helicopter Engine with 1.5, 2.5 & 3mm hex wrenches, decal
            sheet and instruction manual

REQUIRES: Fuel: Heli blend with 5-30% nitromethane and 20% lubricant content
          Glow Plug: Long type such as the OS #8
          Glow starter, plug wrench and field equipment

SPECS:    Displacement: .394cu in (6.45cc)
          Bore: 0.850" (21.6mm)
          Stroke: 0.693" (17.6mm)
          Practical R.P.M.: 2,000-17,000
          Output: 1.35 BHP/16,000 RPM
          Weight: 10.23oz (290g)

            Carburetor Settings*;
          Needle Valve: Three turns from closed position
          Mixture Metering Screw: 30-45° degrees clockwise
            *Carburetor was preset at factory and requires only small
             adjustments
          Distance/top of cylinder head-bottom of mounting tabs: 2.4" (61.mm)
          Distance/top of cylinder head-bottom of crankcase: 3.03" (77mm)
          Distance between mounting holes same side: 0.60" (15mm)
          Distance between mounting holes opposite side: 1.9" (48mm)
          Cylinder head width: 1.7" (44.6mm)
          Width at mounting tabs: 1.8" (45mm)
          Width of crankcase below mounting tabs: 1.2" (31.1mm)
          Center of engine to front bearing: 1.81" (46.1mm)
          Backplate to front bearing: 2.6" (67.6mm)

                                                                   jxs 10/18/10
                                                                         ir/jxs