I changed my CCT last week with an OEM one and it worked perfect. Now I'm hearing a sound when I take off in first and second too. It's a very soft chirping sound. I only hear it in low rpm's in my first two gears and it goes faster when I go faster. It doesn't happen while sittng still. The sound is not very loud and it's not coming from my forks. It really sounds like birds chirping....

 

since it goes faster as you do, I would check your brakes. My guess is your pads are slightly rubbing the rotor. Next time your out and you hear it, gently apply the front and rear brakes to see if goes away.

If thats not it, I would check to make sure your chain is in good shape and adjusted properly. Make sure its not too tight as this will put stress on your output shaft bearing.

If thats not it, I check to make sure you dont have excess play in wheel bearings. I wouldnt think its the bearings unless you have a lot of miles on it.... like 40,000. but its worth checking out.

I would guess the sound is there after second gear. your just moving fast enough that the wind noise is louder than the chirp and you no longer hear it.