The following steps are taken to decarbonise the engine :

Remove the exhaust muffler.

• Disconnect the spark plug.
• Remove the intake pipe bolt.
• Loosen the bolt detaching the left side cover from the cylinder head.
• Remove the bolt and left side cover.
• Remove the gearshift pedal.
• Remove the left crankcase cover.
• Rotate the generator rotor counterclockwise and align the "T" mark on the generator rotor with the index mark on the left crankcase.
• Make sure that the "O" mark on the cam sprocket is aligned with the index mark on the cylinder head cover.
• Remove the cam sprocket bolts.
• Remove the cam chain by lifting it up with the screw driver.
• Remove the cam sprocket.
• Remove the cylinder head nuts.
• Remove the cylinder head cover.
• Remove the 6mm bolt attaching the cylinder head and cylinder.
• Remove the cylinder head.
• Remove the spark plug.
• Check the spark plug for cracks at the outer and inner insulator.
• Remove the valve adjuster hole caps.
• Remove the bolts and the cylinder head right side cover.
• Screw an 8 mm bolt to the rocker arm shaft and pull out each rocker arm shaft.
• Remove the rocker arm.
• Remove the cam shaft.
• Compress the valve spring compressor and remove the retainer, valve spring and valve.
• Remove the carbon deposits from the combustion chamber.
• Remove any gasket material from the contact face of the cylinder head.
• Clean both intake and exhaust valves thoroughly to remove carbon deposits.
• Apply a light coating of valve grinding paste to each valve face. Lap each valve and seat using a rubber hose or other hand-lapping tools.
• Remove the valve and inspect the face.
• Measure the valve seat.