Honda ACF110CBTR Owner's Manual page 92

Maintenance Fundamentals
Crankcase Breather
Service more frequently when riding in rain, at
full throttle, or after the vehicle is washed or
overturned. Service if the deposit level can be
seen in the transparent section of the drain
tube.
If the drain tube overflows, the air filter may
become contaminated with engine oil, causing
poor engine performance.
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