Cylinder Heads

SAFETY FIRST: Protective gloves and eyewear are recommended at this point.

Removal

Remove both cylinder heads in the same manner.

Drain the coolant. See the Coolant topic for more information.

Remove the carburetors. See the Carburetor Removal topic for more information.

Remove the exhaust system. See the Exhaust System topic for more information.

Remove the spark plugs. See the Spark Plugs topic for more information.

Remove the cylinder head covers. See the Cylinder Head Covers topic for more information.

Remove the camshafts. See the Camshafts topic for more information.

Free the coolant hoses from the cylinder heads.

Remove the cylinder head coolant pipe bolts with an 8 mm socket.

Remove the cylinder head coolant pipes.

Disconnect the petcock and fuel pump vacuum lines (not found on all models) from the intake boots.

Remove the small cylinder head bolt with an 8 mm socket.

Loosen the four large cylinder head bolts evenly with a 14 mm socket.

Remove the large cylinder head bolts and washers.

Tap the cylinder head with a rubber mallet to free it.

Lift off the cylinder head. Take care to not let the cam chain fall into the crankcase.

Remove the head gasket.

Locate the oil pipe, next to the cam chain opening.

Remove the oil pipe from the cam chain opening. Inspect the O-rings and replace them as needed.

Remove the dowel pins.

Remove the front cam chain guide.

Disassembly

To remove the valves see the Valves topic.

Remove the two intake boot bolts with a 5 mm Allen.

Remove the intake boot from the cylinder head.

Inspection

Inspect the front cam chain guide for excessive wear and damage.

Clean the combustion chamber with contact cleaner, a plastic knife, brush and/or rag. Take care to only remove carbon and not scrape the head. Clean away the removed carbon particles with compressed air.

Place a straight edge on the deck of the cylinder head and check for cylinder head warp with a feeler gauge. Check for warp in several places on the head.

Cylinder Head Warpage Limit:  0.05 mm (0.002 in)

Assembly

To install the valves see the Valves topic.

Inspect the intake port and O-ring and replace the parts if needed. Install the intake boot O-ring.

Fit the intake boot to the cylinder head. Install the two intake boot bolts and tighten them securely with a 5 mm Allen.

Installation

Make sure the cylinder head mating surface is clean.

Fit the front cam chain guide into place.

Install the oil pipe. Make sure the O-rings are in good condition.

Install the two cylinder head dowel pins.

Place the new head gasket onto the cylinder.

Install the cylinder head to the cylinder. Guide the cam chain and cam chain guides though the opening in the cylinder head and into the camshaft sprocket area. Remember to keep the cam chain from falling into the crankcase.

Lubricate the threads and seating surface of the large cylinder head bolts with molybdenum disulfide grease. Insert the four large cylinder head bolts with their washers.

The large cylinder head bolts are numbered and they should be tightened evenly and in order in a crisscross manner.

Torque the cylinder head bolts to the fist specification and then the final with a 14 mm socket.

Cylinder Head Bolts (M10)
First Torque: 25 N-m, 2.5 kgf-m, 18 ft-lb
Final Torque: 49 N-m, 5.0 kgf-m, 36 ft-lb

Install the small cylinder head bolt and tighten it to specification with an 8 mm socket.

Connect the petcock and fuel pump vacuum lines (not found on all models) to the intake boots.

Install the cylinder head coolant pipe if it was removed. Use an O-ring in good condition. Tighten the coolant pipe bolt to specification with an 8 mm socket.

Coolant Pipe Bolts: 9.8 N-m, 1.0 kgf-m, 87 in-lb

Connect the coolant hoses from the cylinder head coolant pipes. Tighten the clamps securely.

Install the camshafts. See the Camshafts topic for more information.

Install the cylinder head covers. See the Cylinder Head Covers topic for more information.

Install the spark plugs. See the Spark Plugs topic for more information.

Install the carburetors. See the Carburetor Installation topic for more information.

Install the exhaust system. See the Exhaust System topic for more information.

Fill and bleed the coolant. See the Coolant topic for more information.