Maxijet noise . . . can you help?
 

I just modified my Maxijet 1200. I used the Sureflow Mod kit. Initially I put the largest propeller on but it was too much flow. So I put the smaller prop on ( 1600 gph) but it makes a very loud humming noise. I took it apart and it put it back together but it still makes noise. I actually modified two 1200's but only one makes noise. Will it just go away or is there something I can do about the noise?