Yamaha WR125R 2009 Service Manual page 183

CHAIN DRIVE
Drive chain slack
40.0–50.0 mm (1.57–1.97 in)
ECA13550
NOTICE
A drive chain that is too tight will overload
the engine and other vital parts, and one that
is too loose can skip and damage the swing-
arm or cause an accident. Therefore, keep
the drive chain slack within the specified lim-
its.
4-70