HONDA CR750

Joep Kortekaas' Honda 750 CR kitted race bike

Engine Analysis

Warning: (this is quite a graphic and table intensive page to load,; but worth the wait)

Motor    Power    Inlet System    Exhaust System     Friction and Drag

Restoration Process     Photo Gallery    Joep Koortekaas Page

crkort3.jpg (45106 bytes)

 

 

 

Motor: HONDA CB750R

DATA

CALCULATED RESULTS

Bore

61.5

mm

Piston area of one piston

2,970.58

mm2

Stroke

63

mm

Total piston area

11,882.32

mm2

Capacity of one cylinder

187.1

cm3

Number of cylinders

4

Total capacity

748.6

cm3

Max. piston speed

22

m/s

Engine speed

10,476

rpm

Corr. piston speed 1)

21.7

m/s

Engine speed for max. power

9,600

rpm

Allowable engine speed 2)

10,600

rpm

Piston speed for max. power

20.2

m/s

Inlet opens 3)

20

°BTDC

Inlet closes 3)

47

°ABDC

Inlet duration

247.0

°

Exhaust opens 3)

48

°BBDC

exhaust duration

248.0

°

Exhaust closes 3)

20

°ATDC

Overlap duration

40.0

°

Lobe centre inlet cam

103.5

° ATDC

Inlet valve lift

9

mm

Lobe centre exhaust cam

104.0

° BTDC

Exhaust valve lift

9

mm

Running clearance inlet

0.15

mm

Running clearance exhaust

0.15

mm

1) Based on piston speed times square root of bore over stroke ratio.

2) Using the corrected piston speed.

3) Valve timing is based on 1 mm clearance

Volume of combustion chamber

19.7

cm3

Compression ratio

10.5

:

1

wpe7.jpg (21127 bytes)

 

THE INLET SYSTEM

Inlet valve dia

32

mm

Inlet valve area

804

mm2

Inlet valve seat angle

45

°

Flow coefficient

0.48

Effective valve area

386

mm2

Number of inlet valves

1

Total valve area

804

mm2

Total effective valve area

386

mm2

Velocity of sound

330

m/s

Velocity in valve throat

169

m/s

Mach index

0.47

(Max.=0.5)

Req'd min. inlet valve dia.

32

mm

Max. attainable rpm with

present inlet valve diameter

10,211

rev/min

Carburettor diameter

31

mm

Carburettor area

755

mm2

Number of carburettors per cyl.

1

Total carburettor area

755

mm2

Air velocity in carburettor

79

m/s

Optimum carburettor dia. 4)

31

mm

Max. carburettor diameter 5)

32

mm

4) Based on 81 m/s air velocity.

5) Based on inlet valve area

INLET LENGTH FOR MAXIMUM INERTIA EFFECT

Valve lift when valve area Ames becomes 0.5 cm2

1.47

mm

Inlet closing angle qcs for this valve lift

40

°

Inertia factor Z

1.029

Optimum length 6)

232

mm

6) Actual length of inlet system from bellmouth to valve.

INLET LENGTH FOR MAXIMUM PULSATION EFFECT

Order of pulsation qs

3

Inlet closing angle ABDC

49

°

Optimum length

224

mm

wpeC.jpg (27711 bytes)

 

Motor    Power    Inlet System    Exhaust System     Friction and Drag

Restoration Process

Photo Gallery

Joep Koortekaas Page

Return to CR750 index

Return to Classic Motorcycling Homepage

Copyright: Murray Barnard/Joep Kortekaas - 1999