It's perfectly fine. Just don't forget to bring audio signal through capacitor to the base of transistor. You can also reduce 1k resistor in emiter circuit for 330 or even 220 Ohm to get better range. If you cannot find variable capacitor in 4-40pF range, just put fixed capacitor of ca. 15pF (12-18pF will do). This capacitor should have good thermal stability to reduce drift. To ensure that frequency doesn't interfere with local station(s), just compress or stretch the coil little bit (change the distance between first and last turn of coil). Components are not critical, you can change any of them (in reasonable range). To test oscillator, power the circuit and put it close to FM receiver. Slowly change receivers frequency untill you find spot with perfect silence (no noise). Lift oscillator circuit ca 1/2" or 1cm above table surface and let it drop on table. You should hear loud click form the receiver. (vibrations of the coil upon impact changed frequency of the circuit - thats FM). When you bring audio signal to input of the oscillator circuit, transistor section Base-Collector works like Varicap diode. Audio signal changes potential of the base and this change affects capacity of Base/Collector section of the circuit. This (parasitic) capacitance is part of oscillator circuit (thanks to 0.01uF capacitor between transistor base and top of the oscillator coil). Changing either capacitance or inductance of the oscillator circuit while oscillator is running is changing carrier frequency of the oscillator. Changing frequency of the oscillator is called FM. Simple, isn't it...