Jun 2, 2021 · The Hammerhead GTS 150 top speed has no advertised figure, but owners claim it to be 50 mph (this may still increase depending on mods). Engine Brand Name. Honda GY6 engine. Engine Type. 4-Stroke, single-cylinder, oil-cooled. Carburetion System. Carburetion, 24-mm KF,CB24J x 1. Engine Cooling. Air cooling.