Overhaul

Measuring and reconditioning the cylinder head

Special tools:
998 6052 VALVE SPRING B21 D16 D24 998 6052 Valve Spring B21 D16 D24
999 5219 GRIP TOOL 999 5219 Grip Tool
999 5222 GAUGE 999 5222 Gauge
999 5379 PUNCH 999 5379 Punch
999 5748 Valve compressor B 4164-B 6304 999 5748 Valve Compressor B 4164-B 6304
999 5764 Drift 999 5764 Drift

Note! The illustrations in this service information are used for different model years and / or models. Therefore there may be some variation. However, the essential information in the illustrations is always correct.

Removing valve lifters from the cylinder head





Lift out the valve lifters. Mark up the valve lifters so that the original positions can be established.
Use a suction cup to remove the valve lifters.
Check for wear on the valve lifters. Measure if necessary.
Valve lifters, dimensions: See Specifications Specifications, Mechanical.

Removing valves





Use valve spring compressor 998 6052 VALVE SPRING B21 D16 D24 998 6052 Valve Spring B21 D16 D24 with attachment claw 999 5748 Valve compressor B 4164-B 6304 999 5748 Valve Compressor B 4164-B 6304.

Remove
- the valve locks
- the upper valve collars
- the valve springs
- the valves.

Note! Keep track of the position of the moving parts.

Removing valve stem seals





Use tool 999 5219 GRIP TOOL 999 5219 Grip Tool.
Remove the valve stem seals and the lower valve collars.

Clean the cylinder head:
- the gasket faces
- the combustion chambers
- the inlet and exhaust ports
- the valve seats.

Checking the cylinder head





Clean the spark plug threads (tap M14 x 1.25).
Clean the valves, valve springs and collars.
Visually check for damage.
Regrind the seats if unsure about cracks. See Specifications Specifications, Mechanical.

Checking the cylinder head for distortion

Measure cylinder head distortion Use a steel ruler and feeler gauge. See Specifications Specifications, Mechanical.

Checking for wear in the valve guides





Measure the wear in the valve guides. Use a dial indicator and magnetic holder. Lift the valve approximately 2-3 mm from the seat when carrying out the check.
Clearance between the valve and valve guide: See Specifications Specifications, Mechanical.

Checking the vertical position of the valve stem





Use camshaft adjustment tool 999 5222 GAUGE 999 5222 Gauge.
Position the camshaft adjustment tool in the camshaft bearing recesses.
Measure the height of the valve stem using a feeler gauge through the hole in the camshaft adjustment tool. See Specifications Specifications, Mechanical.

Installing valve stem seals





Lubricate the valve stems and the upper ends of the valve guides.

Install
- the lower valve spring collars
- the valves in their positions.

Install the protective sleeve (included in the gasket kit) on the valve stem.

Note! The protective sleeve must be installed on the valve stem when the valve stem seal is installed.

Lubricate the protective sleeve (1) and install it on the valve stem.





Lubricate the valve stem seal (2).
Press down the seal past the protective sleeve with your finger.
Press the seal down. Use tool 999 5764 Drift 999 5764 Drift. Press down by hand until the tool stops against the lower valve spring washer.
Remove the tool. Pull off the protective socket.

Installing valve springs





Install the valve spring. Install the valve spring washer.
Compress the valve spring so that the three valve lock tracks are visible. Use valve spring compressor 998 6052 VALVE SPRING B21 D16 D24 998 6052 Valve Spring B21 D16 D24 with attachment claw 999 5748 Valve compressor B 4164-B 6304 999 5748 Valve Compressor B 4164-B 6304.

Note! Do not compress more than is absolutely necessary. The valve stem seal may be damaged.

Install the valve locks.
Check that valve locks are in the correct position when the spring is not loaded.
Repeat the procedure with the remaining valves.