Honda CBX Engine

In 1977 the Honda CBX engine was introduced. At the time it was one of the most technologically advanced motorcycle engines on the market. The Honda CBX engine incorporated dual overhead cams with four valves per cylinder.

The engine was designed by Shoichiro Irimajiri, who was highly involved in the 1960’s 250cc moto GP.

At the time of its release in 1977, the Honda CBX was capable of finishing the quarter mile in 11.5 seconds.

This particular fisrt year engine produced about 85 horsepower to the real wheel. (105 horsepower to the crank)

Later models were capable of making higher horsepower numbers. The CBX engine is a 6 cylinder slant 6 setup.

Crank Shaft The engine crank shaft is the heart of the engine. The crank shaft delivers all the engines power to the

transmission which then delivers its power to the wheel. The CBX’s crank shaft is long and has about a 120 degree phase shift between each piston.

Connecting Rods The CBX connecting rods are short, thus allowing for a short stroke. Smaller stroke allows for higher revs. Higher revolutions lead to more power. The CBX engine could redline at approximately 9500 RPM. Higher revolutions mean lower torques.

ENGINE BLOCK The engine Block is the heart and soul of the engine. The engine block houses the pistons, which are encased by the iron piston sleeves. The block is an all aluminum, air cooled housing. Within the block the cast iron heat treated piston

sleeves are press fitted into place to ensure compression and withstand cracking.

Pistons And Sleeves The pistons are connected to the connecting rods. The pistons are then placed inside the head, where the

3 piston rings are placed about 90 degrees apart to ensure compression. A mixture of air and gasoline are forced into the chamber where it is ignited, thus forcing the piston

downwards, and forces the crank shaft to spin. Compression ratio : 9.3:1

Valve train The engine valve train is the system in the engine that allows for the entering and exiting of fuel and

exhaust gasses. The cam shafts sit in the valve train and are connected to the timing chain. When the firing sequence

begins, the cams spin slower than the crank shaft and open the exhaust and intake valve as needed.

Crank Case The engine crank case houses the crank shaft. The crank shaft sits in the crank case and is held in place by its bearing surfaces.

Camshafts The camshafts open and close the intake and exhaust valves for the different stokes of the engine. The cam shafts are lobbed 120 degrees out of phase. Surprisingly, the cams are not held by bearings, they are held in place by replaceable shims.

Performance Specs 1977 engine specs Engine torque specs: Engine speed BHP Torque 2000 10.84 28.73 2500 16.81 35.31 3000 21.66 37.92 3500 26.12 39.20 4000 33.52 44.02 4500 38.54 44.98 5000 44.34 46.58 5500 48.78 46.58 6000 53.97 47.24 6500 57.27 46.27 7000 59.10 44.34 7500 65.61 45.95 8000 68.03 44.66

8500 70.72 43.69

10,000 70.98 37.27

RacingUsed and modified by small groups of racers as a drag bike /pro stock set upCan easily be modified to produce more horsepower by increasing compression ratios,

changing fuel management systems, intake systems, and switching to higher strength internal parts (aftermarket connecting rods, pistons, etc.)

Used by our Rutgers Formula Race Team advisor who professionally races the Honda CBX.Currently has the fastest Naturally aspirated Honda CBX achieving quarter mile times @

9.58 seconds 135mph

Other modifications include Turbo charging and alternative fuels

This particular Honda CBX was modified to run on alcohol

Engine was bored out to 1320 cc, along with high performance pistons and a programmable ECU ( engine control module)

Turbo charger installed giving the bike the ability to achieve a 7.62 seconds @172.9 mph

Problems Encountered Difficulties that occurred while assembling the engine consisted of coordinating individual engine

dimensionsSince each team member individually measured components on their own, differences in rounded

caused misalignment problems.Once our engine parts were fully completed, the hardest task consisted of assembling the

components.Unfortunately, the parts did not all mesh up the first time because some parts were off a couple

thousandths of an inch. These small rounding errors caused a huge dilemma when trying to make connectionsTo solve these problems we spent numerous hours coordinating with the entire team to make all our

dimensions match perfectly. Even still with all our time redefining all the dimensions is everyone's parts, we could not perfectly

dimension ever part to exact specifications. ( This occurred due to drawing parameters and referenced surfaces).