Skoda Workshop Service and Repair Manuals > Roomster > Power unit | 1.2/44; 47; 51; 55 kW MPI engine | Engine cylinder head, valve gear | Repairing the valve gear - Part 2 | Reworking valve seats | Reworking valve seats with NAC milling cutter

Reworking valve seats with NAC milling cutter

–	Place cylinder head on a felt base and secure to prevent it from turning.

–	Match diameter of guide drift to diameter of valve guide.

–	Match diameter of milling cutter to diameter of valve seat.

Valve seat		Ø Milling cutter 90° mm	Ø Milling cutter 120° mm	Ø Milling cutter 60° mm
Inlet valve	Engine BBM, CHFA	36	38	21/34
Inlet valve	BME, BZG, CGPA, CGPB, CEVA, CJLA engine	32	32	21/34
Exhaust valve	Engine BBM, CHFA	30	30	21/34
Exhaust valve	BME, BZG, CGPA, CGPB, CEVA, CJLA engine	30	30	21/34

Milling sequence

1 -	Mill valve seat with 90° milling cutter until a perfect contact pattern is achieved. (Do not exceed maximum permissible reworking dimension!)

2 -	Chamfer top correction angle with 120° milling cutter until the valve seat diameter -a- ( → Chapter) is achieved.

3 -	Mill bottom correction angle with 60° milling cutter until valve seat width -c- ( → Chapter) is achieved.

–	Grind in valve/valve seat with fine grinding paste so as to achieve a perfect contact pattern -arrows-.

–	Check contact pattern e.g. with water colour (perfect contact pattern over entire circumference).

–	Install valve springs.

–	Inspect valves for tightness.

The tightness of the valves can be checked by filling petrol into the inlet and outlet canal (no petrol must flow out at the valve seat).

After the repair measure the dimension -h- again and calculate the maximum permissible reworking dimension → Chapter.

Note

If the reworking dimension is exceeded, proper operation of the valve gear is no longer assured and the cylinder head must be replaced.

Skoda Workshop Service and Repair Manuals