This is good it can bolt up to the 5:1 gearbox. However check out these ststs:
Total Displacement: 41.5cc
Bore: 40 mm
Stroke: 33 mm
Piston Rings: 2
Compression: 7.5
Carburetor: Walbro WYK-93
Oil Mixture: 40:1
Horsepower: 1.97 hp at 7500 rpm
Torque: 1.66 lb ft at 5500 rpm
Clutch Diameter: 78 mm
Spark Plug: NGK BM7A
Approx Idle RPM: 2500 rpm
Approx Max RPM: 12000
Weight: 6.5 lbs (2.96kg)
Although it can go up to 12k rpm it should never be pushed to that. That's 12k under no load or long duration. It has a max hp of 1.97 at 7500 rpm; once you go over that hp will begin to diminish under load. After you get beyond max hp the contributing factors to speed then become aerodynamics, weight reduction, gravity, terrain surface and wind direction. Still I do like this engine.