Honda CRF250F Owner's Manual Installation And Operation page 133

Modifications
We strongly advise you not to remove any
original equipment or modify your
motorcycle in any way that would change its
design or operation. Such changes could
seriously impair your motorcycle's
handling, stability and braking, making it
unsafe to ride.
Removing or modifying your exhaust
system (such as the spark arresters or
mufflers) or other equipment can also make
your motorcycle illegal.
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