I think Mehmet wants to do a precision speed control closing the loop with an F-to-V convertor which itself is fed with the pulses from an encoder.

Since you want to get going with the LM2917, did you first try to calibrate it by feeding the range of frequencies that it will finally see in real time? And the output must be closely scaled to match the command range - this activity ( of matching the user command and feedback ) is the first step in such closed loop setups.

Raghu