BMW 5251 Service Manual page 295

Camshaft Timing chain/
Fit top sprocltet to primary timing chain and install on exhaust
camshaft so that pointer (arrow) on sprocltet lines up with
cylinder head sealing surface.
Position sprocket so that chain slack is on tensioner rail side.
4
Insert BMW special tool 11 4 220 in cylinder head and screw
in adjustment screw by hand just until it contacts tensioning
rail and chain slack is removed.
NOTE-
BMW special tool 7 1 4 220 is an adjustable primary chain
tensioner that simulates the function of the tensioner.
-
Make sure arrow on top primary sprocket is still lined up with
upper edge of cylinder head. Reposition sprocket if neces-
sary.