Makita DCS6400 Owner's And Safety Manual page 20

Pull the chain (6) around the sprocket nose (8) of the guide bar
in the direction of the arrow.
Guide the chain over the chain catch (9).
Pull the guide bar as shown by the arrow to take the slack
out of the chain, so that it comes up to the bottom edge of the
guide bar (10).
Line up the holes in the sprocket guard (3) with the bolts (11).
Turn the chain tensioning screw (H/13) until the chain tensioning
bolt (12) is aligned with the hole in the guide bar.
Replace the sprocket guard.
Manually tighten the retaining nuts (H/2).
Tightening the saw chain
Slightly lift the end of the guide bar and turn the chain adjusting
screw (13) to the right (clockwise) until the chain rests against
the bottom side of the guide bar.
While still holding up the tip of the guide bar, tighten the retaining
nuts (2) with the universal wrench.
NOTE:
Before tightening the chain, loosen the two nuts (2) slightly.
20
6 8
9 10
11
3
2
13
E
F
12
G
H