Take off the cylinder head 11 12 100.
Remove the oil sump 11 13 000.
Take off the connecting rod big end bearing cap with the rod at BDC.
When installing: Both connecting rod and bearing cap are marked
to indicate the correct cylinder.
Connecting rod 1 is at the chain sprocket end.
The cylinder reference or machining numbers must always be on the same side.


11 12 100
11 13 000

Press out the piston and connecting rod upwards.
When installing: The piston ring end gaps should be displaced
trough 180° in relation to one another.
The arrow on the piston crow should point towards the timing chain end.

Remove the gudgeon pin.
When installing: The gudgeon pin is matched to its piston and should
not be interchanged.
The oil drillway in the connecting rod small and boss should be on the side
indicated by the arrow on the piston.
Warning: Use only pistons of identical make and weight group.
The weight group is indicated by + or - stamped on the piston crow.

Piston identificatin:

BMW 2,5 CS	A = 36 mm (1.42 in)
BMW 2800 CS	A = 31.8 mm (1.25 in)
BMW 3,0 CS	A = 31.8 mm (1.25 in)
BMW 3,0 CSi	A = 31.8 mm (1.25 in)

Check piston installed clearance¹.
Measure at point A for Mahle pistons:

BMW 2,5 CS	20.5 mm	(0.807 in)
BMW 2800 CS	14.7 mm	(0.579 in)
BMW 3,0 CS	14.5 mm	(0.571 in)
BMW 3,0 CSi	14.6 mm	(0.575 in)

Measure at point A for KS piston:

BMW 2,5 CS	26.25 mm	(1.033 in)
BMW 2800 CS	24.05 mm	(0.947 in)
BMW 3,0 CS	24.05 mm	(0.947 in)
BMW 3,0 CSi	24.05 mm	(0.947 in)

Measure at point A for Nüral pistons:

BMW 2,5 CS

16.2 mm

(0.638 in)

Measure at point A for for Alcan piston:

BMW 2800	18.5 mm	(0.728 in)
BMW 3,0 CS	21.4 mm	(0.843 in)
BMW 3,0 CSi	17.5 mm	(0.689 in)

See technical data