10. Honda CB 750 K7 - CRANKSHAFT/ CONNECTING ROD

CRANKSHAFT/ --

10• CONNECTING ROD ~ HONDA

~ CB750

1.8-2.2kg-m (13.0-15.9ft-lbs)

~1

2.0-2.5kg-m(14.5-18.1 ft-lbs)

10-0

~ HONDA

~ CB750 CRANKSHAFT/CONNECTING ROD

TROUBLESHOOTING 10-2
SERVICE INFORMATION 10-2
CRANKSHAFT REMOVAL 10-3
CONNECTING ROD REMOVAL 10-4
CRANKPIN OIL CLEARANCE INSPECTION 10-4
CONNECTING ROD ASSEMBLY 10-8
CRANKSHAFT ASSEMBLY 10-8

10-1

CRANKSHAFT/CONNECTING ROD ~ HONDA

TROUBLESHOOTING ~ CB750

Excessive Noise
1. Cran~shaft
-Excessive crankshaft journal bearing play
-Excessive crankpin bearing play

SERVICE INFORMATION

WORKING PRACTICE

All bearing inserts are selective fit and are color coded .
Select replacement bearing from color code table.

SERVICE DATA Standard Service Limit

Item 35.985-36.000 mm (1.4167-1.4173 in.) 35.940 mm (1.4150 in.)
Crankshaft 35.940 mm (1 .4150 in.)
35.985-36.000 mm (1.4167-1.4173 in.) 0.05mm (0.0020 in.)
Journal 0 .D. 0.40mm (0.0157 in.)
Crank pin O.D. 0 - 0.03 (0-0.0012 in.)
Runout 22.75mm (0.8957 in.)
Connecting rod side clearance 0.15-0.30 mm (0.0059-0.0118 in.) 0.08mm (0.0031 in.)
Crankcase
Upper case crankshaft holder width 22.85-22.90 mm (0.8996-0.9016 in.)
Crankshaft oil clearance 0.020-0.046 mm (0.0008-0.0018 in.)

10-2

~HONDA CRANKSHAFT/CONNECTING RO"O

~ CB750

CRANKSHAFT

REMOVAL

If necessary, remove the cylinder head,
cylinder and pistons.
Separate the crankcase.

NOTE
When the pistons are not removed,
remove the connecting rod big end
bearing caps.

Remove the mainshaft from the primary
drive chains.
Take out the crankshaft together with the
primary drive chains.

UPPER CRANKCASE INSPECTION

Measure the. journal holder width of the
upper crankcase.

SERVICE LIMIT: 22.75 mm (0.8957 in.)

CONNECTING ROD SIDE
CLEARANCE

Inspect the connecting rod side clearance
on the crankpin.

SERVICE LIMIT: 0.40 mm (0.0158 In.)

10-3

Q.\ HONDA

CRANKSHAFT/CONNECTING ROD ~ CB750

CONNECTING ROD
REMOVAL

Loosen connecting rod cap nuts.
Remove the connecting rod bearings, and
check for wear or damage.

CRANKSHAFT INSPECTION

Measure the crankshaft for runout.
SERVICE LIMIT : 0.05 mm (0.0020 In.)

CRANKPIN OIL
CLEARANCE
INSPECTION

Assemble the connecting rod inserts in
each rod cap. Place a plastigauge strip
across each crankpin.

NOTE
Clean all oil from the bearing inserts
and crankpins.
Install each connecting rod on the
corresponding crankpin and torque to
specifications.
TORQUE: 1.8-2.2 kg-m (13.0-15.9ft-lbs)

10-4

W'\HONDA CRANKSHAFT/CONNECTING ROD

~ CB750

Remove the caps and measure the
plastigauge with the scale on the gauge
bag.

SERVICE LIMIT: 0.08mm (0.0032 in.)

CRANKSHAFT JOURNAL OIL
CLEARANCE

Put the lower bearing inserts in place and
install the crankshaft. Put a piece of
plastigauge across each journal, avoiding
oil holes.

NOTE
Wipe clean oil from the bearings and
journals.

Install the lower crankcase. Install the
mounting bolts and torque them evenly.

TORQUE: 2.0-2.5 kg-m (14.5-18.1 ft-lbs)

Remove the caps and measure the
compressed plastigauge on each journal.
SERVICE LIMIT: 0.08 mm (0.0032 In.)
If the clearance exceeds the limit, the
bearings should be replaced.

10-5

~HONDA.

CRANKSHAFT/CONNECTING ROD ~ CB750

CRANKPIN BEARING SELECTION

Determine and record each crankpin O.D.
code number stamped on the crankweight
on the drive sprocket side (or measure the
crankpin O.D.)

Record the corresponding connecting rod I.D.
code number (or measure it).

Cross reference the crank and bearing
codes in the chart to determine the replace-
ment bearing color.

®

! !/y,::::::r.t--L: 3 3 4 3

Crankpin

Con- 0.0 4 5
necting 35.995- 35.990-
36.000-
rod big 35.995 35.990 35.985
end 1.0. B (Brown) A (Black)
B (Brown)
3 39.024 C (Green) B (Brown) ......___
-39.016 ,----------,
0 (Yellow) C (Green) (2) GENERATOR SIDE
39.016 L1 _C__(G__r_e_e_n_),
- 39.008 (3)COLOR CODES
0 (Yellow)
39.008
- 39.000

Inspect the crankpin oil clearance.

STANDARD: 0.020-0.046 mm
(0.0008-0.0018 In.)

10-6

~HONDA CRANKSHAFT/CONNECTING ROD

~ CB750

CRANKSHAFT JOURNAL BEARING
CLEARANCE

Determine and record the main journal O.D.
code letter stamped on the crankweight on
the drive sprocket side.

Determine and record the corresponding Q)
upper crankcase bearing support code L:IAABBB!
letter.

Cross reference the bearing support and
crank codes to determine the replacement
bearing color.

( I )UPPER CRANKCASE (Z)LOWER CRANKCASE

B

(1)CONTACK

BREAKER SID A

A 1-----, C ~ .....(2)GENERATOR SIDE
36.000- 35.990-
lB : ~0 . ~;4: APPLY THIN COATING OF
35.995 35.985 ( ) MOLYBDENUM
B (Brown) L-----• y;;J) fl
A (Black)
C (Green) 35.995 -
35.990
D (Yellow)
B (Brown)

B 39.016 C (Green) B (Brown)
- 39.008
,-- -~--.
: A : 39.008
t_ ____J - 39.000 C (Green) ~ DISULFIDE GREASE

Inspect the main bearing clearance. (3)COLOR ~
CODES
STANDARD: 0.020-0.046 mm
(0.0008-0.0018 In.)

10-7

(;if\ HONDA

CRANKSHAFT/CONNECTING ROD ~ CB750

CONNECTING ROD a
ASSEMBLY
" D,F,J"
Prior to assembly, ensure that the connect-
ing rods have the same weight code letter.
There are three weight code letters, D, F
and J.

Install the bearing inserts, and bearing
caps .

CAUTION
Be sure bearing caps are installed in
their correct location and the bearing
pawls point to the front of the
engine. Torque the cap bolts.

TORQUE: 1.8-2.2kg-m (13.0-18.1 ft-lbs)

CRANKSHAFT
ASSEMBLY

Check that the oil holes are not clogged .

Install the spark advancer shaft , 0 -ring and
oil seal.

Install the bearing inserts.

Install the gears and assemble the upper
and lower crankcases .
TORQUE : 2.0-2.5 kg-m (14.5-18.1ft-lbs)

10-8