Honda CBR650 - Service manual > Service information

GENERAL

• This section covers service of the cylinder head, valves and camshafts.
• All the services covered in this section can be done with the engine installed in the frame.
• When disassembling, mark and store the disassembled parts to ensure that they are reinstalled in their original locations.
• Clean all disassembled parts with cleaning solvent and dry them by blowing them off with compressed air before inspection.
• Camshafts lubricating oil is fed through oil passages in the cylinder head and camshaft holder. Clean the oil passages before assembling them.
• Be careful not to damage the mating surfaces when removing the cylinder head cover and cylinder head.

Troubleshooting

• Engine top-end problems usually affect engine performance. These problem can be diagnosed by a compression test or by tracing engine noises to the top-end with a sounding rod stethoscope.
• If the performance is poor at low speeds, check for white smoke in the crankcase breather hose. If the hose is smoky, check for a seized piston ring.

Compression too low, hard starting or poor performance at low speed

• Valves:
  • Incorrect valve clearance adjustment
  • Burned or bent valve
  • Incorrect valve timing
  • Broken valve spring
  • Uneven valve seating
• Cylinder head:
  • Leaking or damaged cylinder head gasket
  • Warped or cracked cylinder head
  • Loose spark plug
• Worn cylinder, piston or piston rings.

Compression too high, overheating or knocking

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

Excessive smoke

• Cylinder head:
  • Worn valve stem or valve guide
  • Damaged stem seal
• Worn cylinder, piston or piston rings.

Excessive noise

• Cylinder head:
  • Incorrect valve clearance adjustment
  • Sticking valve or broken valve spring
  • Damaged or worn camshaft
  • Loose or worn cam chain
  • Worn or damaged cam chain
  • Worn or damaged cam chain tensioner
  • Worn cam sprocket teeth
• Worn cylinder, piston or piston rings.

Rough idle

• Low cylinder compression

Component location

Cylinder compression test

Warm the engine to normal operating temperature.

Stop the engine and remove the all spark plug caps and spark plugs.

Install a compression gauge [1] into the spark plug hole.

Turn the ignition switch ON with the engine stop switch "".

Shift the transmission into neutral.

Open the throttle all the way and crank the engine with the starter motor until the gauge reading stops rising.

The maximum reading is usually reached within 4 - 7 seconds.

Compression pressure:
1,500 kPa (15.3 kgf/cm2, 218 psi) at 300 min-1 (rpm)

Low compression can be caused by:

• Blown cylinder head gasket
• Improper valve clearance adjustment
• Valve leakage
• Worn piston rings or cylinder

High compression can be caused by:

• Carbon deposits in combustion chamber or on piston head

Cylinder head cover

REMOVAL/INSTALLATION

NOTE:

• The cylinder head cover can be serviced with the engine installed in the frame.

Disconnect the spark plug caps from the spark plugs.

Remove the throttle body..

Disconnect the crankcase breather hose [1] from the cylinder head cover.

Pull off the heat guard rubber [2] from the PAIR check valve cover joints [3].

Remove the cylinder head cover bolts [1] and mounting rubbers [2].

Remove the cylinder head cover [3] from the cylinder head.

NOTE:

• Do not forcibly remove the dowel pins from the cylinder head cover.

Remove the cylinder head cover packing [1] from the cylinder head cover.

Installation is in the reverse order of removal.

TORQUE:
Cylinder head cover bolt:
10 N*m (1.0 kgf*m, 7 lbf*ft)

NOTE:

• Replace the cylinder head cover packing with a new one.
• Install the cylinder head cover packing into the groove in the cylinder head cover.
• Apply sealant (TB5211C manufactured by ThreeBond, KE45 manufactured by Shin-Etsu Silicone or an equivalent) to the cylinder head cover packing semi-circular areas as shown (8 places).
• Check the mounting rubbers [2] are in good condition, replace them if necessary.
• Install the mounting rubbers with their "UP" mark [3] facing up.

Adjust the throttle grip freeplay.

See also: