What as difference in crf150f and crf150r?

Answer 1

The CRF150F is a trail bike, soft suspension, not as much power as the r, air cooled engine. The CR150R is the motorcross version, more power (21 hp), water cooled, taller suspension, less low end power, you have to keep it at high rpm's to get all the power. They are quite different.

Answer 2

A cr dirt bike is a two stroke. A crf is a four stroke, hence the f.