BMW 5251 Service Manual page 264

[camshaft Timing Chain
<
While pressing down on secondary timing chain tensioner
install locking tool (BMW 11 3 292) or a similar pin.
NOTE-
Two types of secondary timing chain tensioners are used,
with either two holes (shown) or a single hole for the locking
pin tool.
-
Remove intake and exhaust sprockets together with
secondary chain.
<
Remove secondary timing chain tensioner bolts
(arrows)
and remove tensioner.
-
Remove primary timing chain sprocket from exhaust
camshaft.
-
Remove sprocket and hang timing chain from end of exhaust
camshaft.
4
Remove secondary chain guide bolts
(arrows)
and remove
guide.