The Honda CBX EngineBy: MAE 388 Design Team 5

A.Kerner, T.Doehner, J.Doyle, N.KarasModel Year: 1979

Key Advantages• Double-overhead cams power 24 valves which feed the motor

through constant velocity carburetors • Only two inches wider than the four cylinder Honda CB750 it

replaced, boasting a 5-speed gearbox and svelte clutch• Produces 105 HP (76.6 kW) at 9,000 rpm. For a 500 lb bike, the

power generation is rather remarkable• If today’s sports cars possess a 10:1 weight-to-HP ratio, then the

Honda CBX has a 5:1 weight-to-HP ratio; for 27 year-old technology, this is quite impressive

• First motorcycle engine to boast six cylinder inline configuration, which allows for the bike frame’s size to be smaller as opposed to having a V-6 cylinder configuration

• 6-cylinder configuration allows for a higher top end speed, horsepower and smoothness than previous inline configurations

Key Disadvantages

• Too many moving parts

• Extremely expensive to maintain and is rather heavy

• Carburetors were very hard to maintain properly

Key Features

• There are two individual gears located in the engine’s top center which govern the air intake/exhaust ports:

Piston Firing Order

• The firing sequence for the pistons is: 1,5,3,6,2,4 which leads to maximum power generation per stroke:

Valve Train

• The Honda CBX valve train is very unique in that it guides valves that can be opened/closed dynamically, thus maximizing power output and fuel consumption based on operating conditions

Overall Engine Setup

Disassembly of Engine Setup

Future Improvements & Considerations

• Overall weight reduction, which would directly lead to a more optimal weight-to-HP ratio

• Provide more engine torque by reducing the carburettor size

• Electronic ignition

References

• www.honda.com

• www.bikez.com

• www.cbxworld.com

• www.chuckhawks.com