This is the Thunder Tiger RL-53H Redline Helicopter Engine. REDLINE is a new engine product line of Thunder Tiger. High performance is one of the main features of the Redline series engine.
Specification:
Displacement: 8.27 cc. / 0.529 cu. in.
Bore: 22.5 mm. / 0.886 in.
Stroke: 21.8 mm. / 0.858 in.
Practical RPM: 2,000 ~ 21,000
Output: 2.1 BHP / 17,000 RPM
Weight: 380 g. / 13.40 oz.

With the largest displacement in the .50 size engine category. The XC2 extreme composite coating with nano-technology from Japan enhances engine performance. The all-new designed carburetor is mounted to the crankcase with a heat insulator to keep the carburetor working at stable temperature in different conditions.
All Thunder Tiger engines have been designed to combine high performance with easy handling and maintenance using CAD computer technology, resulting in consistent high quality and reliability. Subjected to rigorous quality control check ensures that it will provide years of trouble free use.
Features
Biggest displacement with the most power for 50 class RC helicopters Fix type carburetor installed with thermal isolator gasket construction
Ringed piston with XC2 cylinder construction
Push-pull throttle lever
Anodized CNC-Manufactured heat-sink head
RR ball bearing
Reinforced beam structure
Redline R3 glow plug included
Thunder Tiger