3. Honda CB 750 K7 - INSPECTION & ADJUSTMENT

JINSPECTION &

ADJUSTMENTS •

SERVICE INFORMATION 3-1 CARBURETOR SYNCHRONIZATION 3-11 El
ENGINE OIL 3-2 DRIVE CHAIN 3-12
OIL FILTER ELEMENT 3-2 BATTERY 3-13
OIL FILTER SCREEN 3-3 BRAKE FLUID 3-13
CRANKCASE BREATHER 3-3 BRAKE SHOE/PAD WEAR 3-14
AIR CLEANER 3-4 BRAKE PEDAL 3-14
FUEL LINE 3-4 STOPLIGHT SWITCH 3-15
SPARK PLUG 3-5 HEADLIGHT AIM 3-15
VALVE CLEARANCE 3-5 CLUTCH LEVER FREE PLAY 3-16
CONTACT BREAKER POINTS 3-6 SIDE STAND 3-17
IGNITION TIMING 3-7 SUSPENSION 3-17
CAM CHAIN TENSIONER 3-8 RETIGHTENING BOLTS AND NOTS 3-17
THROTILE OPERATION 3-8 WHEELS/SPOKES 3-17
CARBURETOR ADJUSTMENT 3-9 STEERING HEAD BEARING 3-17
CARBURETOR CHOKE 3-9 OIL PRESSURE 3-18
FAST IDLE 3-10 CYLINDER COMPRESSION 3-18

SERVICE INFORMATION

SPECIFICATIONS

Spark plug gap, (ND)X24ES·U, (NGK)D8EA : 0.6-0.7 mm (0.024-0.028 in.)
Ignition timing "F" mark: 15° BTDC at 1,200 rpm
43° BTDC at 4,500-5,350 rpm
Full advance: 0.05 mm (0.0020 in.)
Valve clearance IN : 0.08 mm (0.0032 in.)
2-6 mm (0.08-0.24 in.)
EX: 1,000 ± 100 rpm
Throttle free play: 200-240 mmHg
Idle speed : 1,000 2,500 ± 500 rpm
Synchronization vacuum:
Fast idle speed: 13 ± 1 kg/cm2 (185 ± 14 psi)
Compression:
Clutch free play: 10-20 mm (3/8-3/4 in.)

Rear brake free play (K·Model): 20-30 mm (3/4-1-¼·in.)
Drive chain slack: 20 mm (3/4 in.)

TORQUE VALUES 1.2-1.9 kg-m (8.7-13.7 ft-lbs)
1.0-1.4 kg-m (7.2-10.1 ft-lbs)
Spark plug 1.1-1 .5 kg -m (8.0-10.9 ft-lbs)
Tappet hole cap 2.7-3.3 kg-m (19.5-23.9 ft-lbs)
Tappet adjusting locknut 3.5-4.5 kg-m (25.3-32.5 ft-lbs)
Oil filter center bolt 8.0-10.0 kg-m (57.9- 72.3 ft-lbs)
Oil drain bolt
Rear axle nut

3-1

~ HONDA.

INSPECTION & ADJUSTMENTS ~ CB750

ENGINE OIL (1) OIL TANK

OIL LEVEL CHECK ---(2) UPPER LEVEL

Warm up the engine to the normal \
operating temperature. Stop the engine and
place the motorcycle on the centerstand. i

ICAUTION ...... - - - -(3) LOWER LEVEL

If the oil pressure light does not go out,
stop the engine immediately as severe
engine damage may result.
If the engine has just been operated at
high RPMs, idle the engine at least 30
seconds before stopping the engine to
prevent a low reading.

Check the level with the dipstick. Do not // 3)01LFILTER
screw in the dipstick to check the level. I~ - ---=-- _ / L ~ ~ - - - - - - - t (

If the level is below the lower oil level mark ' f'C,... . (2) ENGINE OIL DRAIN BOLT
on the dipstick, raise to the upper level 3.5-4.5kg-m(25 .3-32 .5ft-lbs)
mark . W JO
(1)01L TANK DRAIN BOLT
OIL CHANGE .. -~ l--15• i-...
Remove the oil tank drain bolt, crankcase
drain bolt, and oil filter element cover to =rw ...~ - o• ,,
drain the oil.
SAE 10W I
After draining the oil tank and the crank-
case, operate the kick starter pedal several Ll
times to force out all residual oil remaining
in the oil system passages. 2:.:J2.7-3.3 kg-m

Check the operation of the bypass valve in 1·9·:a-=-:"('11
the oil filter bolt.
1
NOTE
Check that the drain plug seals are in (1) F MODEL
good condition .

When the oil has been completely drained,
reinstall the crankcase and oil tank drain
plugs, and oil filter element cover.
Fill the oil tank with approximately 2.01(2.1
U.S.qt.) of recommended grade oil.
Start the engine and operate for a few minutes.

Stop the engine, refill the oil tank with oil
while checking the oil level with the filler
cap dipstick.

OIL QUANTITY: 3.51
RECOMMENDED OIL: SAE 10W-40

OIL FILTER ELEMENT

Change the oil when the oil filter element is
replaced .

3-2

~ HONDA INSPECTION & ADJUSTMENTS

~ CB750

OIL FILTER SCREEN

Drain the oil from the crankcase and oil
tank.
Remove the oil pan (page 2-3).

Clean the oil filter screen in/with solvent.

NOTE
• Do not forget to install the neu t ral

switch cord clamp during reassembly.
• Replace the filter screen if damaged

or broken.

CRANKCASE
BREATHER

The blow-by gas is returned to the com -
bustion chambers through the breather
tube , breather separator and intake pipe.
Check that the breather tube is clean and is
not clogged.

Remove the left side cover, chain protector
and silicon rectifier.

Remove the breather element case and
take out the element.

Clean the element in solvent and dry.
Reinstall the element.

NOTE
Note the installation direction of the
breather case tube as shown.

(1) SOLVENT

3-3

INSPECTION & ADJUSTMENTS ~ HONDA.

AIR CLEANER ~ CB750

Remove the two air cleaner mounting bolts
and remove the air cleaner lower case.

Clean the lower case and element .

(1 ) CLEANER ELEMENT

Clean the element by tappling it lightly to
loosen dust. Then , blow away the remainin-
ing dust from the outer surface by applying
compressed air from the inside of the
element.

Replace the element with new one if fouled
excessively or broken or damaged .

FUEL LINE

Check all fuel lines for leaks or damage.
Open the fuel cock to make sure that the
fuel filter screen is not clogged .

3-4

~ HONDA INSPECTION & ADJUSTMENTS
~ CB750

SPARK PLUG (2) DAMAGE

Remove the spark plugs, and check the (3) DAMAGE

electrodes and cent er porcelai ri for

deposits, eroded electrodes, or carbon
fouling .

If the spark plug is carbon or wet fouled,
clean with a stiff wire brush or in a spark
plug cleaner.

STANDARD SPARK PLUGS:
AMERICAN MODEL: (NGK) DBEA

(ND) X24ES-U
CANADIAN MODEL: (NGK) DRBES-L

(ND) X24ESR-U

Adjust the spark plug gap to 0.6-0.7mm

(0.024-0.028in.).

NOTE
When installing the spark plug, it should
be screwed in finger tight and then
torqued with spark plug wrench a
further 112 to 3/4 turn to compress the
washer.

VALVE CLEARANCE

CAUTION
The valve clearance adjustment must be
performed while the engine is cold.

Remove the fuel tank, valve adjusting hole
caps and point cover.
Rotate the crankshaft clockwise slowly
until the n1 cylinder inlet valve tappet goes
down all the way and then starts to lift.
Check that the 1.4 cylinder "T" mark aligns
with the index mark (in this position, the :t1
cylinder is at T.D.C . of the compression
stroke .)
Check the valve tappet clearance for the
valves marked with black dots.

CYLINDER No. ++ 1 +i:2 +l'.3 :!t4 (1) ADJUSTING SCREW
EX 0
0 3-5
•• • •IN 0 0

Rotate the crankshaft 360° further until the

"1.4 T" mark aligns with the index mark (in

this position, the#4 cylinder is at T.D.C. of

compression stroke).

Check the valve tappet clearance for the

valves marked with white dots.

STANDARD:

IN: 0.05 mm (0.0020 In.)

EX: 0.08 mm (0.0032 in.)

If necessary, adjust by loosening the

adjusting screw lock nut and turning the

screw until there is slight drag on the feeler

gauge. Retighten the lock nut.

Recheck the clearance with the feeler

gauge.

INSPECTION & ADJUSTMENTS ~ HONDA

~ CB750

CONTACT BREAKER (2) PITIED
POINTS
(1) CORRECT ('3) REPAIR OR REPLACE
FILING (4)0UT OF

Remove the point cover. Open the points ALIGNMENT (5) BURNED (6) METAL TRANSFER
with finger or small screwdriver blade and
examine for pitting. If pitted or burned,
replace the points. A gray discoloration is
normal and can be removed with a point
file. Clean the point contacts after filing
with a clean piece of unwaxed paper such
as a business card , or with chemical point
cleaner.

ADJUSTMENT (1 ) (7) REPLACE

Rotate the crankshaft in the clockwise 1/
direction to find the position where each
breaker point gap is at maximum and check :1/(2)LOCK ING
using a feeler gauge. To adjust the point SCREW
gap, loosen the contact breaker plate
locking screws and move the contact (1) YELLOW LEAD
breaker plate to achieve correct gap.
Retighten the locking screws.

NOTE
Make sure that the feeler gauge is free of
oil or grease.

Ignition timing adjustment must be
performed when the contact breaker point
gap is adjusted.

REPLACEMENT

If the points are pitted or burned, or if
adjustment becomes impossible, replace
the points with new ones.

After installing, perform the point gap and
ignition timing adjustments.

CAUTION
Reconnect the point leads properly as
illustrated.

3-6

Ci}\ HON'DA INSPECTION &ADJUSTMENTS

~ CB750

IGNITION TIMING

Contact breaker point gap must be
adjusted before the ignition timing
adjustment is performed .

DYNAMIC TEST WITH SERVICE (3) SCREW @
TESTER: (2) RETARD

Connect the service tester as shown . Run
the engine at 1000 rpm idle speed.

INSPECTION

(1) Connect the timing light to the it 1, jj: 4
cylinder breaker points. The timing for
the it 1, it 4 cylinders is correct if the
"F " 1.4 mark aligns with the index mark.

(2) Connect the timing light to the jt 2, it 3
cylinder breaker points. The timing for
the jt 2, jt 3 cylinders is correct if the " F"
2.3 mark aligns with the index mark.

(3) Run the engine at 2500 rpm and check
that the index mark is within the
advance marks.

ADJUSTMENT (1 ) ADVANC~ _,...--::::~:::--.....
<:,
(1) Loosen the three base plate locking
screws @ and carefully rotate the base (5) BASE PLATE @

plate ® until the "F"1.4 mag<-- aligns (6) ADVANCE
(7) RETARD
with the index mark.
(2) Loosen the two base plate locking (10) SCREW @ (8) SCREW ~
(9) SCREW @
screws © and carefully rotate the base
ADJUSTMENT
plate ® until the "F" 2. 3 mark aligns
with the index mark. (1) Rotate the crankshaft slowly to align
(3) Check the advancer if the index mark is "F" 1.4 mark with the index mark. Loosen
not within the advance marks. (Refer to
page 16·4) the three base plate locking screws ®

STATIC TEST WITH BUZZER and carefully rotate the base plate @
TESTER: until the buzzer starts sounding. Re·
tighten the base plate locking screws @
(1) After connecting the buzzer tester,
rotate the crankshaft slowly in the (2) With the "F" 2.3 mark aligned with the
clockwise direction to align the "F" 1.4 index mark, loosen the two base plate
mark with the index mark. The timing locking screws @ and rotate the base
for the it 1,jt4 cylinders is correct if the
buzzer sounds when both marks align . plate® until the buzzer starts to sound.
Retighten the locking screws @ . Check
(2) Rotate the crankshaft 180° further and that the timing is correct by rotating the
check that the buzzer sounds when the crankshaft several times.
"F" 2.3 mark aligns with the index mark.

3-7

INSPECTION & ADJUSTMENTS {:;jJ\ HONDA

CAM CHAIN ~ CB750
TENSIONER
(1) LOCK NUT
Start the engine and set the idling speed to
900-1,000 rpm . Loosen the tensioner lock
nut and the tensioner bolt. When these are
loosened, the cam chain tensioner will
automatically position itself to provide the
correct cam chain tension. Retighten the
tensioner bolt and lock nut .

(2) ADJUSTING BOLT

THROTTLE (3) DECREASE PLAY
OPERATION
(4) INCREASE PLAY
THROTTLE GRIP FREE PLAY (1) ADJUSTER

ADJUSTMENT

Return the choke knob fully. The standard

throttle grip free playis 2-6 mm (0.0787-
0.2362 in) measured at the throttle grip

flange.
To adjust, loosen the throttle grip adjuster
_lock nut and turn the throttle grip adjuster.
Tighten the lock nut after adjustment.
Major adjustment is made with lower
adjuster at the carburetor.

OVERRIDING STROKE

Return the choke knob fully. Twist the
throttle grip outward until a resistance is
felt and measure the travel of the grip from
the point of resistance to the full stop
position. This travel (overriding stroke)
should be 3.2-6.4 mm (0.1260-0.2520 in.)
Adjustment is made by adjusting the
carburetor idle speed and synchronization
adjustment. Replace the throttle return
cable if adjustment cannot be made.

(1)ADJUSTING NUT ~

+

(3)1NCREASE PLAY

3-8

~ HONDA INSPECTION & ADJUSTMENTS

~ CB750

CARBURETOR
ADJUSTMENT

Start and warm up the engine for several
minutes. Set the engine idle speed to
1,000 :t 100 rpm by the adjusting stop screw.

IDLE SPEED: 1,000 :t 100 rpm

If the proper idle speed cannot be obtained,
turn in the pilot screw until it lightly seats,
and then back it out to specification.

F-MODEL: 1 ¾ TURNS OUT
K-MODEL: 1 ½ TURNS OUT
Set the engine idle speed to 1,000 ±100rpm
by turning the stop screw.

S CARBURETOR CHOKE

Check the choke knob play by observing
the movement of the choke link.
Adjustment is made by turning the choke
cable mounting screw.

y 3-9

INSPECTION & ADJUSTMENTS ~ HONDA

Adjust the force with which the choke knob ~ CB750
is operated by turning the knob.

FAST IDLE l f (1) ADJUSTING SCREW

Start the engine and move the choke knob •
to obtain the highest idle speed.
FAST IDLE SPEED: 2,750 ±750 rpm
With the choke knob pulled all the way, turn
in the adjusting screw until it contacts the
choke cam.

Return the choke knob fully and screw in
the adjusting screw 1½-2 turns further.

D

3-10

Ci

~ HONDA INSPECTION & ADJUSTMENTS

~ CB750

,o

r

CARBURETOR
SYNCHRONIZATION

Adjust the throttle grip free play. Warm the ergine to operating temperature.

Install the vacuum gauge adaptors, and connect a set of four vacuum gauges to the adaptors.

Start the engine and check the vacuum balance between the carburetors.

STANDARD: 24-28cmHg

Set the engine idle to 1,000±100 rpm by turning the stop screw.

Synchronize the carburetors with the adjusters using the u2 carburetor as the reference.

(2) FUEL

•

-/

TTACHMENT A (l7 ·
rrT/CHMENT B ~1

NOTE
To raise the vacuum, turn the adjuster in

the direction ® . To lower the vacuum,

turn the adjuster in the direction@.
To increase the engine speed, turn the

screw in the direction ®. To lower the

engine speed, turn the stop screwfo the

direction G).

3-11

INSPECTION & ADJUSTMENTS r:::ifJ\ HONDA
~ CB750

DRIVE CHAIN )( )(

CAUTION I (1) DAMAGE (2) WEAR

The service life of the drive chain is 0
dependent upon proper lubrication
and adjustment. (3) NORMAL

Place the motorcycle on its center stand,
with the transmission in neutral and
ignition switch off.

Turn the rear wheel slowly, and inspect the
drive chain and sprockets for damage,
excessive wear or any other defects. Drive
chain with damaged rollers, loose pins, or
missing 0-rings must be replaced .

DRIVE CHAIN LUBRICATION OR

Clean the drive chain in/with light oil and EMMI
wipe off excess oil.
(REPLACE) (NEW)
CAUTION (1) RED ZONE (1) REDZONE
Do not use a steam cleaner as this will
ruin the 0-rings. (2) GREEN ZONE

Lubricate the drive chain with clean engine
oil or grease.

CAUTION I

Do not use solvent spray chain lubricant
as such practice will result in damaged
0-rings.

DRIVE CHAIN TENSION

Move the chain up and down with fingers
and measure the amount of slack at a point
midway between the drive sprocket and the
rear wheel sprocket.
STANDARD SLACK: 15-25 mm (5/8-1 in)
Remove the cotter pin from the rear axle
nut, and loosen the nut. Loosen the lock
nuts on both adjusting bolts. Turn both
adjusting bolts an equal number of turns
until the correct drive chain tension is
obtained. Replace the chain if the fork ends
enter the red zone.

AXLE NUT TIGHTENING TORQUE:
8-0-10.0kg-m (57.9- 72.3 ft-lbs)
Retighten the axle nut, install the cotter
pin, and retighten the adjusting bolts.
Check that the rear wheel rotates freely by
tu ring it by hand .

3-12

~ HONDA INSPECTION & ADJUSTMENTS

~ CB750

r,.

BATTERY
ELECTROLYTE

Check that the battery electrolyte level is
maintained between the upper and lower
level marks on the side of the battery. If the
electrolyte level is low, carefully add
distilled water until the electrolyte level in
each cell is between the upper and lower
level marks.

Wash the battery with water, if necessary.
Clean around the terminals.
Check the specific gravity of the electrolyte
if the starter, turn signals or any other
electrical accessaries do not operate
properly.

BRAKE FLUID ( I) UPPER LEVEL

LEVEL CHECK

Before removing the reservoir cap,
ensure that the reservoir is horizontal.
Do not operate the brake lever with
the reservoir cap removed as this will
force the brake fluid out of the reser-
voir. Avoid spilling brake fluid on
painted surfaces.

Whenever the level is lower than the level
mark engraved inside the front reservoir or
lower level mark on the rear reservoir,
check the brake pads for wear. Fill" the
reservoir with DOT3 BRAKE FLUID from a
sealed container, to the proper level. If the

r--. brake pad wear does not exceed the limits,

this will usually indicate fluid leak which
should be repaired.

CAUTION I

Do not mix different brands of brake
fluid as they are not compatible. Stay
with one fluid as specified in this
manual.

REPLACEMENT

The brake fluid absorbs moisture in the air
and must be replaced at regular intervals.

AIR BLEEDING

The brakes must be bled when the lever or
pedal becomes soft or spongy, or when the
lever or pedal travel is excessive.

3-13

INSPECTION & ADJUSTMENTS ~HONDA

~ CB750

BRAKE SHOE/PAD (1)RED LINE
WEAR

Inspect the pads to determine the pad
wear. If any pad is worn to the red line,
replace all front or rear pads as a set.

(2) RED LINE

BRAKE SHOE INSPECTION
(K-MODEL)

"*"Check the brake shoes for wear. If the
arrow on the wear indication aligns

with the reference mark "Y" on the brake

panel on full application of the rear brake,

inspect the brake shoes and replace them if

the service limit is exceeded.

BRAKE PEDAL

(K-MODEL)

To adjust the rear brake, turn the adjusting
nut. .

BRAKE PEDAL FREE PLAY: 20-30 mm

(0.8-1.2 In.)

3-14

~HONDA INSPECTION & ADJUSTMENTS

~ CB750

STOPLIGHT SWITCH

NOTE
The stoplight switch adjustment must
be performed after the brake pedal
play and height have been adjusted.

BRAKE PEDAL HEIGHT
ADJUSTMENT:

Clearance between the brake pedal arm and
the foot rest should not be less than 5 mm
(1/4 in.).

Adjust the stoplight switch so that the
stoplight will come on when the brake
pedal is depressed to the point where the
brake just starts to engage.

NOTE
The front brake stoplight switch need
not be adjusted .

To adjust, turn the switch adjusting nut in
orout.

HEADLIGHT AIM

Remove the side marker reflectors and
check that the punch marks on the
headlight case are aligned with the marks
on the cover.

The horizontal beam adjustment is made
with the adjusting screw located on the left
side of the headlight. Turning the screw
clockwise will focus the beam toward the
left side of the rider and turning the screw
counterclockwise will focus the beam
toward the right side.

3-15

INSPECTION & ADJUSTMENTS ~ HONDA

CLUTCH LEVER FREE ~ CB750
PLAY.

Inspect the clutch lever free play .
FREE PLAY: 10-20 mm (0.4-0.8 in.)

ADJUSTMENT P LAY

Loosen the lock nut and turn t he clutch V
cable adjuster, located at the clutch lever,
until the correct free play is obtained . (4)DECREASE

NOTE (1) LOCK NUT
Do not expose the adjusting bolt
threads more than 8 mm (0.32 In).

If the adjustment cannot be made with the
clutch lever adjuster, screw the adjuster all
the way into the clutch lever bracket, and
then turn the clutch cable adjuster, located
at the clutch housing, to loosen the clutch
cable.

Remove the clutch cover, loosen the clutch
lifter adjusting screw lock nut, and turn the
clutch adjusting screw until a slight
resistance is felt. From this position, turn
the clutch adjusting screw in the

counterclockwise direction 1/4-1/2 turn.

Turn the clutch cable adjusting bolt at the
clutch housing side of the engine so that
there is approximately 20 mm (0.8 In.) of
free play at the end of the clutch lever, then
tighten the lock nut. The remaining clutch
lever free play is obtained by the clutch
cable adjusting bolt.

NOTE
Do not expose the adjusting bolt
threads more than 17 mm (0.6693 In.)

After the adjustment has been made.check
to see that the clutch is not slipping and
that the clutch is properly disengaging .

3-16

~HONDA INSPECTION & ADJUSTMENTS
~ CB750

SIDE STAND

Check the side stand spring for loss of
tension and damage. Check the rubber pad
for deterioration or wear. Replace if wear
extends to the wear line as shown.
Check the side stand assembly for freedom
of bend , breakage or any other defects.

SUSPENSION (1) WEAR

Check the front fork assembly by locking LIMIT LINE
the front brake and pumping the fork up
and down vigorously. Suspension action ,.
should be smooth and there must be no oil
seepage or squealing . ...J

Check the rear suspension hardness by

r pushing down on the seat. Adjustment is
made by turning the adjusters.

Check all sliding surfaces for damage or
signs of leaks.

Pump grease through the grease fitting at
the rear fork pivot. Check the rear fork
bushing for excessive wear.

RETIGHTENING FUMiM
BOLTS AND NUTS

Retighten all bolts and nuts to the
specified torque.

WHEELS/SPOKES

Check the wheels for damage to the rims
and spokes. Check for loose spokes. (only
K-Model) Check rim runout.

(F-MODEL)
CAUTION
COMSTAR WHEEL does not require
retightening.

SPOKE TIGHTENING TORQUE:

0.3-0.4kg-m (2.2-2.9 ft-lbs)

STEERING HEAD
BEARING

Raise the front wheel off the ground and
turn the handlebar full right and left to see
that it moves freely.

Check the steering head by locking the
front wheel and moving the motorc;:ycle
back and forth . There must l;>e no play or
rattle in the steering stem.

3-17

INSPECTION & ADJUSTMENTS ~ HONDA

OIL PRESSURE ~ CB750

Connect the oil pressure gauge.
Check the oil level.
Start the engine and run at 3,000 rpm .
STANDARD: 3.5-4.5 kg/cm2 (49.8-64.0psl)
Check that the oil pressure warning lamp
goes out. If the oil pressure warning lamp
keeps on, stop the engine immediately and
isolate the cause.

CYLINDER
COMPRESSION

• Start the engine and run at idle speed until the engine speed stabilizers.
• Remove all spark plugs.
• Connect the adaptor of the compression gauge to any spark plug hole.
• Open the choke valve fully by pushing in the choke knob.
• Open the throttle grip fully.
• Crank the engine with the starter and read the highest pressure indicated by the gauge.
• Repeat the above procedure to the remaining cylinders.

CYLINDER COMPRESSION: 10.0-12.0 kg/cm 2 (142.2-170.7 psi)

CAUTION

Make sure that there is no compression
leak.

Low cylinder compression usually indi-
cates:
• Improper valve tappet clearance High compression readings may be
• Leaky valve ascribable to carbon deposits in the com-
• Blown cylinder head gasket busion chambers or on the piston heads.
• Worn piston rings

3-18