Page 9-1

SERVICE INFORMATION	9-1
TROUBLESHOOTING	9-2
CYLINDER HEAD COVER REMOVAL	9-3
CAMSHAFT REMOVAL	9-3
CYLINDER HEADS	9-7
VALVE GUIDE REPLACEMENT	9-11
VALVE SEAT INSPECTION/REFACING	9-12
CYLINDER HEAD ASSEMBLY	9-14
CYLINDER HEAD INSTALLATION	9-15
CAMSHAFT INSTALLATION	9-17
CYLINDER HEAD COVER INSTALLATION	9-20

SERVICE INFORMATION

GENERAL

The cylinder heads can be removed without removing the engine.
Camshaft lubricationg oil is fed through an oil pass pipe. Be sure the holes in the oil pass bolts are not clogged.
Durring assembly apply MoS₂ paste grease to the camshaft holders, camshaft journals of the cylinder head, rocker arm shafts, rocker arm slipper faces and valve stems to provide initial lubrication.

SPECIFICATIONS

Unit: mm (in)

ITEM				STANDARD	Service limit
Compression pressure				1,324 ± 196 kPa (13.5 ± 2.0kg/cm², 192 ± 28 psi)	---
Camshaft	Cam lobe height	IN		38.189 (1.5035)	38.17 (1.503)
	Cam lobe height	EX		38.213 (1.5044)	38.19 (1.504)
	Journal O.D.			21.959-21.980 (0.8645-0.8654)	21.95 (0.864)
	Runout			0.030 (0.0012)	0.05 (0.002)
	Oil Clearance			0.040-0.093 (0.0015-0.0037)	0.11 (0.004)
Rocker arm	Rocker arm I.D.	IN/EX		12.000-12.018 (0.4724-0.4731)	12.03 (0.474)
Rocker arm	Rocker arm shaft O.D.	IN/EX		11.966-11.984 (0.4711-0.4718)	11.96 (0.471)
Valve and valve guide	Valve stem O.D.	IN		5.475-5.490 (0.2156-0.2161)	5.47 (0.215)
	Valve stem O.D.	EX		6.555-6.570 (0.2580-0.2587)	6.55 (0.258)
	Valve guide I.D.	IN		5.500-5.512 (0.2165-0.2170)	5.53 (0.218)
	Valve guide I.D.	EX		6.600-6.615 (0.2598-0.2604)	6.66 (0.262)
	Stem-to-guide clearance	IN		0.010-0.037 (0.0004-0.0015)	0.07 (0.003)
	Stem-to-guide clearance	EX		0.030-0.060 (0.0014-0.0024)	0.11 (0.004)
	Valve seat width			0.9-1.1 (0.035-0.043)	1.5 (0.06)
	Valve guide pro- jection height	IN		19.4-19.6 (0.76-0.77)	---
	Valve guide pro- jection height	EX		17.9-18.1 (0.70-0.71)	---
Valve spring	Free length	OUTER	IN	42.14 (1.659)	40.58 (1.598)
		OUTER	EX	42.83 (1.686)	41.25 (1.624)
		INNER	IN	38.11 (1.500)	36.47 (1.436)
		INNER	EX	38.81 (1.765)	37.51 (1.477)
Cylinder head warpage				---	0.10 (0.004)

TORQUE VALUES

Cylinder head cover bolt		10 N•m (1.0 kg-m, 7.2 ft-lb)
Camshaft holder	8 mm bolt	23 N•m (2.3 kg-m, 17 ft-lb)
	8 mm nut	23 N•m (2.3 kg-m, 17 ft-lb)
	6 mm bolt	10 N•m (1.0 kg-m, 7.2 ft-lb)
Cylinder head	10 mm nut	48 N•m (4.8 kg-m, 35 ft-lb)
	8 mm bolt	23 N•m (2.3 kg-m, 17 ft-lb)
	8 mm nut	23 N•m (2.3 kg-m, 17 ft-lb)
	6 mm bolt	10 N•m (1.0 kg-m, 7.2 ft-lb)
Camshaft sprocket bolt		10 N•m (1.0 kg-m, 7.2 ft-lb)
Cam chain tensioner bolt		10 N•m (1.0 kg-m, 7.2 ft-lb)
Oil pass pipe	7 mm bolt	10 N•m (1.0 kg-m, 7.2 ft-lb)
Oil pass pipe	8 mm bolt	23 N•m (2.3 kg-m, 17 ft-lb)

TOOLS

Special
Valve guide reamer (IN)	07984—2000001 or 07984—200000B (U.S.A. only)
Valve guide reamer (EX)	07984—ZE20001 or 07984—ZE2000B (U.S.A. only)
Valve guide driver attachment (IN)	07943—MF50100
Valve guide driver attachment (EX)	07943—MF50200

Common
Valve guide driver, 5.5 mm (IN)	07742—0010100
Valve guide driver, 6.6 mm (EX)	07742—0010200 or 07942—6570100 U.S.A. only
Valve spring compressor	07757—0010000 or 07957—3290001

Valve seat cutter		(Not available in U.S.A)
Cutter holder	IN 5.5 mm	07781—0010101
Cutter holder	EX 6.6 mm	07781—0010201
Flat cutter	IN 28 mm (32°)	07780—0012100
Flat cutter	EX 35 mm (32°)	07780—0012300
Interior cutter	IN 30 mm (60°)	07780—0014000
Interior cutter	EX 37.5 mm (60°)	07780—0014100
Seat cutter	IN 27.5 mm (45°)	07780—0010200
Seat cutter	EX 35 mm (45°)	07780—0010400

TROUBLESHOOTING

Engine top-end problems are usually performance-related and can usually be diagnosed by a compression test.
Engine noises can usually be traced to the top-end with a sounding rod or stethoscope.

Uneven or low compression

Valves
- Incorrect valve adjustment
- Burned or bent valves
- Incorrect valve timing
- Broken valve spring
Cylinder head
- Leaking or damaged head gasket
- Warped or cracked cylinder head
Cylinder and piston (Refer to section 10)

High compression

Excessive carbon build-up on piston crown or combustion chamber.

Excessive noise

Incorrect valve adjustment
Sticking valve or broken valve spring
Damaged or worn rocker arm or camshaft
Loose or worn cam chain
Worn or damaged camn chain tensioner
Worn cam sprocket teeth

Poor idling

Compression too low

CYLINDER HEAD COVER REMOVAL

Remove the following parts:

seat
fuel tank (page 4-3)
air cleaner case (page 4-4)
thermostat bolts
radiator mounting bolts, and swing the radiator forward

NOTE

If you will be servicing the inner cylinder head cover components, remove the carburetors (page 4-5) at this time.

FRONT:

Disconnect the spark plug caps.

Remove the cylinder head cover bolts and cover.

NOTE

If the cylinder head cover is difficult to remove:
Remove the radiator mounting bolts and release the radiator
from the frame grommets. Suspend the radiator with a
piece of rope or something suitable. (refer to page 9-8).

REAR:

Disconnect the spark plug caps.
Remove the cylinder head cover bolts and cover.

Remove the cylinder head covers (page 9-3) and carburetors (page 4-5).
Remove the timing hole cap and crankshaft hole cap from the left crankcase cover.
Align the FT mark (rear: RT mark) on the flywheel with the index mark on the left crankcase cover timing hole by turning the crankshaft counterclockwise.

Page 9-4

Make sure the piston is at TDC (TOP DEAD CENTER) on the compression stroke so the cam lobes are all facing down.

If the cam lobe is facing up at TDC, turn the crankshaft 360° couterclockwise, and re-align the mark and notch.

Pull wedge A straight up while holding wedge B down.
Secure wedge A with a 2 mm pin as shown.

Remove the camshaft holder on the cam sprocket side by removing the two mounting bolts.

Remove the cam sprocket bolt, rotate the crankshaft counterclockwise one turn (360°) and remove the other cam sprocket bolt.

NOTE

Be careful not to let the cam sprocket bolts fall into the crankcase.

Remove the three camshaft holder mounting bolts and the nut, the oil plate and the holder.

Page 9-5

Remove the dowel pins.
Hang the cam chain on the camshaft behind the camshaft flange and remove the cam sprocket while lifting the camshaft out.

Attach a piece of wire to the cam chain to prevent it from being dropped into the crankcase.

INSPECTION

Cylinder head

Inspect the camshaft holder and cylinder head journal surfaces for scoring or evidence of insufficient lubrication.

Camshaft runout

Support both ends of the camshaft with V-blocks and check the camshaft runout with a dial indicator.

SERVICE LIMIT: 0.05 mm (0.002 in)

Using a micrometer, measure the height of each cam lobe.

SERVICE LIMIT:
IN: 38.17 mm (1.503 in)
EX: 38.19 mm (1.504 in)

Check the camshaft journals for wear or damage.
Measure the O.D. of each journal.

SERVICE LIMIT: 21.95 mm (0.864 in)

Page 9-6

Camshaft bearing oil clearance
Wipe any oil from the journals. Lay a strip of plastigauge lengthwise on top of each camshaft journal.

NOTE

Avoid placing plastigauge over the oil hole.

Install the camshaft holders and tighten the mounting bolts in a crisscross pattern in 2 or 3 steps.

NOTE

Do not rotate the camshaft when using plastigauge.

TORQUE:
   6 mm flange bolt: 12 N•m (1.2 kg-m, 9 ft-lb)
   8 mm flange bolt: 23 N•m (2.3 kg-m, 17 ftlb)
   8 mm flange nut: 23 N•m (2.3 kg-m, 17 ft-lb)

Remove the camshaft holder and measure the width of each plastigauge. The widest thickness determines the oil clearance.

SERVICE LIMIT: 0.11 mm (0.004 in)

When the service limit is exceeded, replace the camshaft and recheck the oil clearance.

Replace the cylinder head and camshaft holder if the clearance still exceeds the service limit.

Camshaft holder/Rocker arm shaft/Rocker arm
Remove the rocker arm shafts by tapping the holder with a soft hammer.

Page 9-7

Remove the rocker arms and wave washers from the shafts.

Inspect the rocker arm shafts and rocker arms for wear or damage.

Check the rocker arms for clogged oil holes.

Measure the O.D. of each rocker arm shaft.

SERVICE LIMIT:
IN/EX: 11.96 mm (0.471 in)

Measure the l.D. of each rocker arm.

SERVICE LIMIT: 12.03 mm (0.474 in)

CYLINDER HEAD

REMOVAL

NOTE

The cylinder head can be removed with the engine installed.

Drain the coolant (page 5-3) and remove the following:

camshaft (page 9-3)
exhaust pipes

California model only:
Remove the ASV pipes from the cylinder head.

Disconnect the clutch cable from the clutch lifter arm by removing the clutch cable holder bolt.
Remove the oil pipe from the engine.

NOTE

Do not bend the oil pipe during removal.

Remove the water pipes.

Page 9-8

Remove the cam chain tensioner mounting bolts and washers from the cylinder head and cylinder.

Loosen the 6 mm bolt, 8 mm bolts, 8 mm nut and 10 mm nuts/washers in a criss-cross pattern in 2 or three steps.
Remove the bolts and nuts.

FRONT:

Remove the radiator mounting bolts.
Release the radiator from the frame grommets and suspend it with a piece of rope or something suitable.
Remove the upper exhaust port stud to allow frame clearance for cylinder head removal.
Lock two 8 mm nuts together on the stud to aid in removal.

Remove the rear cylinder head.

REAR:

Remove the rear cylinder head.

Remove the gasket, dowel pins, and cam chain guide from the cylinder.

Page 9-9

DISASSEMBLY/INSPECTION

Cylinder head

CAUTION

Avoid damaging the gasket surfaces

Check the spark plug hole and valve areas for cracks.
Check the cylinder head for warpage with the straight edge and feeler gauge.

SERVICE LIMIT: 0.10 mm (0.004 in)

Remove the valve spring cotters, retainers, springs, and valves using a Valve Spring Compressor.

TOOL:
Valve spring compressor	07757—0010000 or 07957—3290001

CAUTION

To prevent loss of tension, do not compress the valve springs more than necessary to remove teh cotters.

NOTE

Mark all parts during disassembly so they can be placed back in their original locations.

Remove the valve stem seals and valve spring seats.

Remove carbon deposits from the combustion chamber.

Valve springs
Measure the free length of the inner and outer valve springs.

SERVICE LIMITS:
	INNER (IN): (EX):	36.47 mm (1.436 in) 37.51 mm (1.477 in)
	OUTER (IN): (EX):	40.58 mm (1.598 in) 41.25 mm (1.624 in)

Replace the springs as a set if they are shorter than the service limits.

Page 9-10

Valve stem-to-guide clearance
Inspect eac valve for bending, burning, scratches, or abnormal stem wear.

Check valve movement in the guide and measure and record each valve stem O.D.

SERVICE LIMITS: IN: 5.47 mm (0.215 in)
EX: 6.55 mm (0.258 in)

Measure and record each valve guide I.D.

NOTE

Ream the guides to remove any carbon deposits before checking clearances.

SERVICE LIMITS: IN: 5.53 mm (0.218 in)
EX: 6.66 mm (0.262 in)

Subtract each valve stem O.D. from the corresponding guide I.D. to obtain the stem to guide clearance.

SERVICE LIMITS: IN: 0.07 mm (0.003 in)
EX: 0.11 mm (0.004 in)

If the stem-to-guide clearance exceeds the service limits, determine if a new guide with standard dimentions would bring the clearance within tolerance. If so, replace any guides as necessary and ream to fit.

TOOLS:
IN:	07984—2000001 or 07984—200000B (U.S.A. only)
EX:	07984—ZE20001 or 07984—ZE2000B (U.S.A. only)

NOTE

It is important that the reamer always be rotated in the same direction when it is inserted or removed.

If the stem-to-guide clearance exceeds the service limits with new guides, also, replace the valves.

NOTE

Reface the valves seats whenever the valve guides are replaced.

Page 9-11

VALVE GUIDE REPLACEMENT

Chill the valve guides in the freezer section of a refrigerator for about an hour.
Heat the cylinder head to 212°F (100°C) with a hot plate or oven. Maximum allowable temperature is 300°F (150°C).

WARNING

To avoid burns, wear heavy gloves when handling the heated cylinder head.

CAUTION

Do not use a torch to heat the cylinder head; it may cause warping.

Support the cylinder head and drive out the old guides from the combustion chamber side of the cylinder head.

TOOLS:
Valve guide driver
(IN):	07742—0010100
(EX):	07742—0010200 or 07942—6570100 (U.S.A. only)

NOTE

Avoid damaging the cylinder head.

Make note of the valve guide projection specifications (following), then drive in new guides from camshaft side of the cylinder head.

TOOLS:
Valve guide driver
5.5 mm (IN):	07742—0010100
6.6 mm (EX):	07742—0010200
Attachment
5.5 mm (IN):	07943—MF50100
6.6 mm (EX):	07943—MF50200

VALVE GUIDE PROJECTION HEIGHT:
IN:	19.4 - 19.6 mm (0.76 - 0.77 in)
EX:	17.9 - 18.1 mm (0.70 - 0.71 in)

Ream the new valves guids after installation.

NOTE

Use cutting oil on the reamer during this operation.
It is important that the reamer always be rotated in the same direction when it is inserted or removed.

Clean the head thoroughly after reaming the valve guides.

TOOLS:
Valve guide reamer
IN:	07984—2000001 or 07984—200000B (U.S.A. only)
EX:	07984—ZE20001 or 07984—ZE2000B (U.S.A. only)

Page 9-12

VALVE SEAT INSPECTION/REFACING

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

Apply a light coating of Prussian Blue to each valve seat. Lap each valve and seat using a rubber hose or other hand lapping tool.

Remove and inspect each valve.

CAUTION

The valves cannot be ground. If a valve face is burned or badly worn or if it contacts the seat unevenly, replace the valve.

Inspect the width of each valve seat.

STANDARD:	0.9 - 1.1 mm (0.035 - 0.043 in)
SERVICE LIMIT:	1.5 mm (0.06 in)

If the seat is too wide, too narrow, or has low spots, the seat must be ground.

VALVE SEAT CUTTERS

Honda Valve Seat Cutters, grinder or equivalent valve refacing equipment are recommended to correct a worn valve seat.

NOTE

Follow the refacer manufacturer’s operating instructions.

VALVE SEAT REFACING

Use a 45 degree cutter to remove any roughness or irregularies from the seat.

NOTE

Reface the seat with a 45 degree cutter when a valve guide is replaced.

Page 9-13

Use a 32 degree cutter to remove the top 1/4 of the existing valve seat material.

Use a 60 degree cutter to remove the bottom 1/4 of the old seat. Remove the cutter and inspect the area you have refaced.

Install a 45 degree finish cutter and cut the seat to the proper width. Make sure that all pitting and irregularities are removed. Refinish if necessary.

Apply a thin coating of Prussian Blue to the valve seat. Press the valve through the valve guide and onto the seat to make a clear pattern.

NOTE

The location of the valve seat in relation to the valve face is very important for good sealing.

Page 9-14

If the contact area is too low on the valve, the seat must be raised using a 60 degree inner cutter.

Refinish the seat to specifications, using a 45 degree finish cutter.

After cutting the seat, apply lapping compound to the valve face, and lap the valve using light pressure.
After lapping, wash all residual compound off the cylinder head and valve.

NOTE

Do not allow lapping compound to enter the guides.

CYLINDER HEAD ASSEMBLY

Install the valve spring seats and new stem seals.
Lubricate each valve stem with MoS₂ paste grease and insert the valve into the valve guide. Turn the valve slowly while inserting to avoid damaging the seals.

Move the valves up and down to check for smooth operation.

Install the valve springs with the tightly wound coils facing the combustion chamber.

Install the spring retainers.

Page 9-15

Compress the springs and install the valve cotters.

CAUTION

To prevent loss of tension, do not compress teh valve springs more than necessary to install the valve cotters.

TOOL:
Valve spring compressor	07757—0010000 or
	07957—3290001

Tap the valve stems gently with a soft hammer to firmly seat the cotters.

NOTE

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

Apply locking agent to the threads of the sealing bolts and tighten them, if removed.

CYLINDER HEAD INSTALLATION

Install the cam chain guide into the cylinder.

Make sure that the cam chain guide bosses are in the grooves of cylinder.

Clean the cylinder head surface of any gasket material.

Install the dowel pins and a new head gasket.

Page 9-16

Install the carburetor insulator on the cylinder head, aligning the boss on the cylinder head with the slot in the insulator.
Tighten the screw securely.

Install the cylinder head.
Reinstall the upper exhaust port stud securely.
Install the 10mm nut/washer, 8 mm nut/washer, 8 mm bolt/washer, and 6 mm bolt and tighten them in a crosscross pattern in 2 or 3 steps.

TORQUE:
	10	mm nut:	48 N•m (4.8 kg-m, 35 ft-lb)
	8	mm bolt:	23 N•m (2.3 kg-m, 17 ft-lb)
	8	mm nut:	23 N•m (2.3 kg-m, 17 ft-lb)
	6	mm bolt:	10 N•m (1.0 kg-m, 7.2 ft-lb)

Install the following:

cam chain tensioner with washers and bolts.
water pipes

TORQUE: Camn chain tensioner bolt:
	10 N•m (1.0 kg-m, 7.2 ft-lb)

Check the oil pass pipe bolts and oil pass pipe for clogging or bending.

Install the oil pass pipe, new sealing washers, oil pass pipe bolts, and the pipe holder bolt.
Tighten the bolts.

TORQUE:
	Oil pass pipe bolt:
		7	mm:	10 N•m (1.0 kg-m, 7.2 ft-lb)
		8	mm:	23 N•m (2.3 kg-m, 17 ft-lb)

Install the following:

camshaft (page 9-17)
camshaft holders (page 9-18)

Page 9-17

California model only:
Install the ASV pipes onto the cylinder.

All models:
install the cylinder head cover (page 9-20)

Reinstall the radiator, and exhaust pipes.

CAMSHAFT INSTALLATION

Apply MoS₂ paste grease to the rocker arm shafts.
Install the rocker arms, rocker arm shafts, and wave washers in the camshaft holders.

NOTE

Install the wave washers in the proper position as shown.

Position the grooves in the rocker arm shafts vertically, aligning the bolt holes of the holder with the holes of the shafts.
Apply MoS₂ grease to the rocker arm slipper faces.

FRONT CAMSHAFT ONLY

Turn the crankshaft counterclockwise and align the “RT” mark on the flywheel with the index mark on the timing hole. Make sure the REAR cam lobes are all facing UP. If they are not, turn the crankshaft counterclockwise one revolution so that the REAR cam lobes are all facing UP. (NOTE: This is the valve overlap position.)

Continue turning the crankshaft counterclockwise (128°) until the “FT” mark on the flywheel aligns with the index masrk on the timing hole (approximately 3/8 turn).

Page 9-18

NOTE

If the front and rear cylinder camshafts were remved, do not confuse them. Check the identification mark on the end of the shaft.

Install the dowel pins into the cylinder head.

Install the camshaft in the cylinder head through the cam chain and install the cam sprocket on the camshaft.

With the cam lobes all facing down, align the timing marks (index lines) on the cam sprocket with the top of the cylinder head.

Place the cam chain on the sprocket.

lnstall the cam sprocket on the camshaft flange and recheck that the timing marks (index lines) align with the top of the cylinder head.

Align the cam sprocket bolt holes in the cam sprocket and camshaft, install and tighten the cam sprocket bolt.

TORQUE: 23 N•m (2.3 kg-m, 17 ft-lb)

Install the holder, oil plate, 8 mm bolts, 8 mm nut and 6 mm bolts.

TORQUE:
	8 mm bolt:	23 N•m (2.3 kg-m, 17 ft-lb)
	8 mm nut:	23 N•m (2.3 kg-m, 17 ft-lb)
	6 mm bolt:	10 N•m (1.0 kg-m, 7.2 ft-lb)

Turn the crankshaft counterclockwise 360° and install the other sprocket bolt.
lnstall the end holder.

CAUTION

Note the direction of the camshaft holder, install the flat surface on the holder facing in.

After installing the front cylinder camshaft, turn the crankshaft counterclockwise 232° (approximately 5/8 turn) and align the RT mark with the index on the timing hole, then install the rear cylinder camshaft using the same procedure as for the front cylinder.

Page 9-19

Lubricate the cam lobes with fresh engine oil.

If the cylinder head was removed with the engine in the frame, install the following:

radiator
exhaust pipe

REAR CAMSHAFT ONLY

Turn the crankshaft counterclockwise and align the “FT” mark on the flywheel with the index mark on the timing hole. Make sure the FRONT cam lobes are all facing DOWN. If they are not, turn the crankshaft counterclockwise one revolution so that the FRONT cam lobes are all facing DOWN.

Continue turning the crankshaft counterclockwise (232°) until the “RT” mark on the flywheel aligns with the index mark on the timing hole (approximately 5/8 turn).

Place the camshaft into correct position with the cam lobes all facing down.
Install the cam sprocket and camshaft holders using the same procedure as for the front cylinder (page 9-17).

FRONT AND REAR CAMSHAFTS

Turn the crankshaft counterclockwise and align the “FT” mark on the flywheel with the index mark on the timing hole.

Install the front camshaft with all the cam lobes facing DOWN. Align the index marks on the cam sprocket with the top of the cylinder head.

Continue turning the crankshaft counterclockwise (232°) until the “RT” mark on the flywheel aligns with the index mark on the tlming hole (approximately 5/8 turn).

Install the rear camshaft with all the cam lobes facing DOWN. Align the index lines on the cam sprocket with the top of the cylinder head.

Page 9-20

Remove the 2 mm pin holding the cam chain tensioner wedge A.

NOTE

Be careful not to let the 2 mm pin fall into the crankcase.
Do not forget to remove the 2 mm pin before installing the cylinder head cover.

CYLINDER HEAD COVER INSTALLATION

Install the cylinder head cover, rubber washer, washer cover, and cylinder head cover bolts.
Tighten the cover bolts.

TORQUE: 10 N•m (1.0 kg-m, 7.2 ft-lb)

Connect the water hose pipe and stall the spark plug caps.
Install the following parts:

Carburetors (page 4-14) (corected page reference)
air cleaner case (page 4-4)
fuel tank (page 4-3)

Fill the cooling system (page 5-3)