6. Honda CB 750 K7 - CYLINDER HEAD/VALVE

CYLINDER HEAD/ ~ HONDA.

6• VALVE ~ CB750

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6-0

W\ HONDA CYLINDER HEAD/VALVE -

~ CB750 •

TROUBLESHOOTING 6-2
SERVICE INFORMATION 6-3
CYLINDER HEAD COVER REMOVAL 6-4
ROCKER ARM AND ROCKER ARM SHAFT REMOVAL 6-4
CAMSHAFT AND CAM SPROCKET REMOVAL 6-5
CYLINDER HEAD REMOVAL 6-8
CYLINDER HEAD DISASSEMBLY 6-10
VALVE GUIDE REPLACEMENT 6-11
VALVE SEAT REPAIR 6-13
CYLINDER HEAD ASSEMBLY 6-15
CYLINDER HEAD INSTALLATION 6-16
CAMSHAFT ASSEMBLY 6-17
ROCKER ARM AND ROCKER ARM SHAFT INSTALLATION 6-18

6-1

CYLINDER HEAD/VALVE ~ HONDA

~ CB750

TROUBLESHOOTING

Engine top-end troubles are usually performance problems which can be diagnosed by a compression test, or noise
problems which can be traced to the top-end of the engine with~ sounding rod or stethoscope.

Low Compression or Uneven Compression
1. Valve troubles

Incorrect tappet adjustment
Burned or bent valves
Incorrect valve timing
Broken valve spring

2. Cylinder head troubles
- Leaking or damaged head gasket
- Warped or cracked cylinder head

3. Cylinder and piston troubles (Refer to
Section 7)

Compression Too High
1. Excessive carbon build-up on piston or combustion chamber

Excessive Noise
1. Incorrect tappet adjustment
2. Sticking valve or broken valve spring
3. Damaged or worn rocker arm or camshaft

4. Loose or worn cam chain
5. Worn or damaged cam chain tensioner
6. Loose balancer chain
7. Worn cam sprocket teeth

6-2

-

~ HONDA CYLINDER HEAD/VALVE

~ CB750

SERVICE INFORMATION

WORKING PRACTICE

All cylinder head maintenance and inspection necessitates engine removal from the frame.
Camshaft lubricating oil is fed to the cylinder head through an oil control orifice located in the engine cylinder head. Be
sure this orifice is not clogged and that the 0-ring and dowel pins are in place before installing the cylinder heads.
During assembling, apply molybdenum disulfide to the camshaft bearings to provide initial lubrication. Pour clean

engine oil into the oil pockets in the cylinder head to lubricate the cams.

SPECIAL TOOLS 07942-3000000
07984-6110000
Valve guide remover (Driver) 07957-3290001
Valve guide reamer (IN/EX) 07908-3230000
Valve spring compressor
Tappet adjusting wrench

SPECIFICATIONS

ITEM STANDARD SERVICE LIMIT

Camshaft and camshaft holder 0.10mm (0.0039 in)
35.86mm (1 .4118 in)
Camshaft bend 0-0.03mm (0-0.0012 in) 35.36mm (1 .3921 in)
21 .890 mm (0.8618 in)
Cam height IN. 36.00mm (1 .4173 in) 22.100 mm (0.8701 in)

EX. 35.50mm (1 .3976 in)

Camshaft holder 0 .0 . 21.939-21 .960 mm (0.8637-0.8646 in)

1.0. 22.020-22.041 mm (0.8669-0.8678 in)

Rocker arm and rocker arm shaft

Rocker arm 1.0. 12.000-12.018 mm (0.4724-0.4731 in) 12.050 mm (0.4744 in)
11.965-11.984 mm (0.4711-0.4718 in) 11 .940 mm (0.4701 in)
Rocker arm shaft 0.0.

Cylinder head 0-0.05mm (0-0.0020 in) 0.10mm (0.0039 in)
Warpage 1.0mm (0.0394 in) 1.5mm (0.0591 in)
Valve seat width

Valve and valve guide

Valve stem O.D. IN. 6.58-6.59 mm (0.2591 -0.2594 in) 6.55mm (0.2579 in)
6.55-6.56 mm (0.2579-0.2583 in) 6.52mm (0.2567 in)
EX. 6.60-6.62 mm (0.2598-0.2606 in) 6.65mm (0.2618 in)

Valve guide I.D. IN/EX

Valve spring free length

Inner 40.30mm (1.5866 in) 39.14 mm (1 .5409 in)
43.05mm (1.6949 in) 41.74 mm (1 .6433 in)
Outer 1.0-1.3mm (0.0394-0.0512 in) 2.0mm (0.0787 in)
10.0-12.0 kg/cm2
Valve face width IN/EX (142.2-170.0 psi)
0.05mm
Cylinder compression 0.08mm (0.0020in)
(0.0031 in)
Valve clearance IN
EX

6-3

CYLINDER HEAD/VALVE ~ HONDA

CYLINDER HEAD ~ CB750
COVER REMOVAL

Remove the engine. (Refer to section 5.)
Unscrew the three 6 mm screws and
remove the breather cover.

Loosen the sixteen 6 mm screws and re-
move the cylinder head cover.

ROCKER ARM AND
ROCKER ARM
SHAFT REMOVAL

Unscrew the two shaft fixing bolts and the
shaft stopper bolt.

6-4

-

~HONDA CYLINDER HEAD/VALVE

~ CB750

Turn the crankshaft so that the two rocker
arms are not contacted by the valves.

Pull the rocker arm shaft out.

Repeat the above procedure on the other
shafts.

NOTE
Mark the rocker arms to insure original
assembly.

CAMSHAFT AND CAM
SPROCKET REMOVAL

Remove the cam chain tensioner holder
from the cylinder.

Unscrew the two cam sprocket mounting 6-5
bolts.

INOTE
Do not drop the bolts into the engine. j
Remove the four cam shaft holder caps .

r

CYLINDER HEAD/VALVE ~ HONDA

Lift the cam chain out of the sprocket and ~ CB750
hang it down over the camshaft on the left
of the cam sprocket.

Remove the camshaft from the cam chain
and cam sprocket.

Hold the cam chain with a piece of wire as
shown not to drop it into the engine.

NOTE
Mark the rocker arms to insure original
assembly.
Remove the camshaft holders from the
cylinder heads.

ROCKER ARM INSPECTION

Inspect each rocker arm for wear or
damage.
Measure the rocker arm I.D.

SERVICE LIMIT: 12.050 mm (0.4744 In.)

NOTE
If any rocker arm requires replacement,
inspect the camshaft for scoring,
chipping, or flat spots on the cam lobe.

6-6

c;}j\ HONDA CYLINDER HEAD/VALVE

~ CB750

ROCKER ARM SHAFT INSPECTION

Measure the rocker arm shaft O.D. at the
rocker arm contacting face.

SERVICE LIMIT: 11.940 mm (0.4701 In.)

BEARING BORE

Install the camshaft holders on the cylinder
head and then install the caps.

NOTE
Ensure that the marking on each cap
agrees with that on the corresponding
holder.

Tighten the camshaft holder cap setting
bolts and nuts.
Torque to 0.8-1.1 kg-m (6.0-8.0ft·lbs).
Measure the vertical directions.

SERVICE LIMIT 22.100 mm (0.8701 In.)

CAMSHAFT BEARING INSPECTION

Measure the camshaft bearing O.D.
SERVICE LIMIT 21.890 mm (0.8618 In.)

6-7

CYLINDER HEAD/VALVE r:;;;}j\ HONDA

CAM HEIGHT ~ CB750

Inspect the cam surfaces for wear or
damage.
Measure the cam height.

SERVICE LIMIT:
INTAKE: 35.86 mm (1.4118 in.)
EXHAUST: 35.36 mm (1.3921 in.)

CAMSHAFT RUNOUT

Set the camshaft on a stand or V blocks.
Set a dial indicator into the center main
journal.

SERVICE LIMIT: 0.10 mm (0.0039 in.)

CYLINDER HEAD
REMOVAL

Remove the sixteen cylinder head nuts and
six 6 mm bolts.

NOTE
Loosen the nuts in the sequence
shown .
Remove the cylinder head from the
cylinder.

6-8

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~ HONDA CYLINDER HEAD/VALVE

~ CB750

Clean carbon deposits from the
combustion chamber.

Check the spark plug holes and valve areas
carefully for cracks.

Clean the head gasket surfaces of any
gasket material

NOTE
Gasket will come off easier if soaked in
solvent.

Clean the head gasket surfaces of any
gasket material with an oil stone.

CYLINDER HEAD INSPECTION 6-9

Check the cylinder head for warpage with a
straight edge and a feeler gauge.

NOTE

i lCheck for warpage in an X pattern.

SERVICE LIMIT: 0.10 mm (0.0039 in.)

r

CYLINDER HEAD/VALVE ~ HONDA

CYLINDER HEAD ~ CB750
DISASSEMBLY

Remove the valve spring cotters, retainers,
springs, and valves .

( I) VALVE SPRING
COMPRESSOR
NO. 07957 -329000 1

VALVE SPRING FREE LENGTH

Measure the valve springsior free length.

SERVICE LIMITS:
INNER: 39.14 mm (1.5409 in.)
OUTER: 41.74 mm (1.6433 in.)

VALVE AND VALVE GUIDE
INSPECTION

Check the valve movement in the guide.
Measure and record each valve stem O.D.
SERVICE LIMITS:

IN: 6.55 mm (0.2579 in.)
EX: 6.52 mm (0.2567 in.)

6-10

~ HONDA CYLINDER HEAD/VALVE
~ CB750

Ream the valve guides to remove any
carbon build-up before checking clearance.

l )VALVE GUIDE
REAMER

N0.07984 -6110000

VALVE GUIDE LO. INSPECTION (!) REMOVAL 12! INSTALLATION

Measure and record each valve guide I.D.
SERVICE LIMIT :6.65mm (0.2618 in)

Subtract each valve stem O.D. from the
corresponding valve guide I.D. to obtain the
stem to guide clearance.
STEM TO GUIDE CLEARANCE
SERVICE LIMITS: IN 0.10 mm (0.0039 In.)

EX 0.13 mm (0.0051 In.)

NOTE
If the stem to guide clearance exceeds
the service limit, determine if a new
guide with standard dimensions would
bring the clearance within tolerance. If
so, replace any guides as necessary
and ream to fit.
If stem-to-guide clearance still exceeds
the service limit with new guides, re-
place the valves and guides.

VALVE GUIDE
REPLACEMENT

Remove the valve guide.

NOTE

I IDo not damage the cylinder head.

Drive the valve guide fully into the cylinder
head .

Ream the new valve guide after installing.

CAUTION
Use cutting oil on the reamer during this
operation.

Clean the cylinder head thoroughly to
remove any metal particles .

6-11

CYLINDER HEAD/VALVE ~ HONDA

VALVE FACE WIDTH AND VALVE ~ CB750
SEAT INSPECTION

Clean all intake and exhaust valves
thoroughly to remove carbon deposits.

Apply a light coating of valve lapping
compound to each valve face.

Lap each valve and seat using a rubber
hose.

Remove the valve and inspect the face.

CAUTION
The valves cannot be ground. If the ace
burned or badly worn, replace the valve.

Measure the width of the valve face
contact.
SERVICE LIMIT : 2.0 mm (0.0787 In.)
If the valve face contact is too wide, too
narrow or has low spots, the valve must be
replaced.

Inspect the seat.

Measure the width of the valve seat.
SERVICE LIMIT :· 1.5 mm (0.0591 In.)
If the seat is burned or badly worn, or too
wide or too narrow, the seat must be
ground.

6-12

~HONDA CYLINDER HEAD/VALVE
~ CB750

VALVE SEAT REPAIR sro~$£Y(2) BLUE I

NOTE >""--..__--t----jJ--~GA1No s·
Follow refacer manufacturer's operat ·
lrig Instructions.

Inspect each cutting stone for crcks. "F" model , 63.5° "F" model
IN 37 mm (1.457 in.)
Reface the cutting stone to the correct IN 34 mm (1 .339 in.)_,___ _ _ EX 34 mm (1 .339 in.)
angle.
EX 32 mm (1 .260 in .) " K" model
NOTE IN 35 mm (1.378 in.)
Each time a stone is removed and " K" model EX 32 mm (1 .260 in.)
reinstalled on the grinder, it must be
refaced on a dressing stand. IN 32 mm (1 .260 in.) "F" model
IN 37 mm (1.457 in.)
SEAT~J~.,.EX29mm(1 .142in.) EX 34 mm (1 .339 in.)
(3) WHITE 1
k~ J " K" model
IN 37 mm (1.457 in.)
EX 34 mm (1 .339 in.)

lnstert the pilot bar into the valve guide
firmly, and lubricate it lightly with thin oil.

(1) VALVE SEAT GRINDER

Use adequate eye protection when using
the valve seat grinder.

Using the blue 37.5 degree stone, remove
1/4 of the existing valve seat material.

6-13

CYLINDER HEAD/VALVE (:;jj\ HONDA

~ CB750

Use the pink 63.5 degree stone and re- (1}0LD SEAT WIDTH
move the bottom 1/4 of the old seat.

Install the white 45 degree finish cut stone
and cut the seat to the proper width.

1 .Omm(0 .0 3 9 4 i n )

63 .5°

Check the contact between the valve and (2)0LD SEAT WIDTH
valve seat using Prussian Blue. If the
contact area on the valve face is too high,
the seat must be lowered , using the blue
37.5 degree stone.

(1}CONTACTTOO HIGH

If the contact area on the valve face is too
low, the seat must be raised, using the 63.5
degree pink cutting stone.

(1}CONTACTTOO LOW

11

6-14

~ HONDA CYLINDER HEAD/VALVE

~ CB750

After cutting the seat, apply lapping com-
pound to valve face, and lap the valve using

light pressure.
After lapping, wash the cylinder head and
valve clean of residual compound.

CYLINDER HEAD (4)NARROW PIT CH ENO
ASSEMBLY

NOTE
Replace the valve stem seals whenever
disassembled.

Lubricate each valve stem with thin oil and
insert the valve in the valve guide.
Install the valve springs and retainers.

CAUTION I

Install the valve springs with the
narrow pitch end facing the cylinder
head.

Install the valve cotters.

CAUTION I

Do not compress the valve spring more
than necessary to install the valve
cotters.

( !} VALVE SPRING

COMPRESSOR
NO. 07957-3290001

6-15

CYLINDER HEAD/VALVE r:::iif\HOND.A

Tap the valve stems gently with a soft ~ CB750
hammer to be certain the cotters are firmly
seated.

CAUTION I

Support the cylinder head above the
work bench surface to prevent possible
valve damage.

CYLINDER HEAD
INSTALLATION

Install the 0-rings, and insert the head
gasket dowels and the head gasket on the
cylinder.

Mount the cylinder head and route the cam
chain .
Torque the mounting nuts and bolts.
12 mm Box Wrench 07906-3230000
TIGHTENING TORQUE: (8 mm Nut)

2.0- 2.5 kg-m(14.5-18.1 ft-lbs)
NOTE
Torque in the numerical sequence
shown.

6-16

~ HONDA CYLINDER HEAD/VALVE
~ CB750

CAMSHAFT ASSEMBLY

Install the camshaft holders.

NOTE
Be sure that the camshaft holder are
correctly located.

Install the camshaft and camshaft
sprocket.

NOTE
Install the camshaft sprocket with the
timing mark to the left.

Position the cam sprocket and cam chain
through the cam shaft from the left side
toward the right.

Position the No. 1 and 4 cylinders to top-
dead-center by turning the crankshaft.
(Aligning the No. 1 and 4 "T" marks on the
spark advancer to the index mark.)

Align the timing index line on the right side
of the camshaft, so that it is parallel to the
top surface of the camshaft holder.

Assemble the cam chain on the cam
sprocket before mounting the cam
sprocket.

The cam sprocket can be mounted on the
camshaft with two sprocket mounting bolts
as shown.

Tightening Torque : 1.8-2.2kg-m
(13.0-15.9ft-lbs)

Install the camshaft holder caps.

CAUTION I

Camshaft holder and cap are matched
sets and can be identified by the identi·
cal numbers stamped on the holder and
cap.

6-17

CYLINDER HEAD/VALVE ~HONDA.

Tighten the bolt and nuts to the specified ~ CB750
torque.
TORQUE: 0.6-1.1kg-m (4.3-8.0 ft·lbs)

Push the push bar in for the cam chain (1) ADJUST! NG SCREW
tensioner.
Install the tensioner on the cylinder and
Loosen the tensioner adjusting bolt.
Retighten the bolt and lock with the lock
nut.
Cam chain adjustment must be performed
after installing the engine.

ROCKER ARM AND
ROCKER ARM SHAFT
INSTALLATION

Turn the crankshaft so that the base circle
of the cam is up.
Install the rocker arm shaft, and install the
mounting bolts.

NOTE
Rocker arms Nos. 1 and 3, and Nos. 2
and 4·, are interchangeable.
Install them correctly.

6-18

~HONDA CYLINDER HEADNALVE

~ CB750

Adjust the valve clearance. (Refer to section 3)

IN: 0.05 mm (0.0020 In.)
EX: 0.08 mm (0.0032 in.)

Pour clean engine oil into the oil pockets in
the cylinder head to lubricate the cams.

Install the cylinder head cover with the
sixteen cross screws.

Install the breather cover with the three
screws.

6-19