Honda CRF250F Owner's Manual Installation And Operation page 194

5. Measure a section of the drive chain to
determine whether the chain is worn
beyond its service limit. Measure the
distance between a span of pins from pin
centre to pin centre. If the distance
exceeds the service limit, the chain is
worn out and should be replaced.
New chain:
Service limit: 638 mm (25.1 in)
Span of pins measured: 41
This motorcycle has a staked master link
drive chain which requires a special tool for
cutting and staking. Do not use an ordinary
master link with this chain. See your dealer.
635 mm (25.0 in)
6. Inspect the sprocket teeth for possible
wear or damage. Replace if necessary.
Damaged Sprocket
Teeth
REPLACE
Normal Sprocket Teeth
GOOD
Standard sprocket sizes:
Drive sprocket
(engine)
13 teeth
If the drive chain or sprockets are
excessively worn or damaged, they should
be replaced. Never use a new chain with
worn sprockets; rapid chain wear will result.
Worn Sprocket
Teeth
REPLACE
Driven sprocket
(rear wheel)
50 teeth
69