Honda NT650 service manual, section 9, Cylinder Head/Valves

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Page 9-0

really big verson

Page 9-1

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)

Page 9-2

TORQUE VALUES

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

TOOLS

Special
har har har... This section is not fun to look at or enter, just a bunch of numbers.
Maybe I'll put a jpg of the tool chart someday.

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

Page 9-3

CYllNDER 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.

CAMSHAFT REMOVAL

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.