Okay, so I’ve seen alot lately of people saying how much they love their Generation Bb’s. I recieved mine from the Whistle Shop a couple weeks ago, and I can see why. I love its tone! Nice and deep, with enough chiff to keep this chiff-lover happy. The problem is that after playing 3 or so tunes, it will suddenly clog up, or SOMETHING. I’ll go to hit the next octave, and nothing will come out but a whoosh of air. Even after patiently blowing out the moisture and trying an arpeggio, it’ll just squeak and blow air. I always end up having to put it aside for at least 5 full minutes, and sometimes it still sucks when I try it again. I always warm it up before playing. I’ve tweaked it as much as I dare, there are definitly no particles in the headpiece that would obstruct windflow… what’s the deal? Has anyone else had this problem? Also, what have you guys done to your Gen Bbs (if anything) to make them sound so good? I’m beginning to wonder if perhaps I just got a bad one…but when it’s behaving well, it sounds really great! Thanks for any help offered.
This doesn’t make any sense, but it’s true. I had an Oak which was like that. It would clog, and there was no way to clear it. One day I accidentally discovered that there were some burrs on the end of the tube. I smoothed them down with sandpaper, and that fixed it. Don’t ask me why.
I checked, and can’t see any burrs anywhere in the tube.. looks like I may be doomed to a bad-but-otherwise-good whistle. 
I am guessing that the alignment between the blade and the windway is a little off.
It sounds like when the fipple is cool, the whistle works. When it warms a bit (and expands, as all things will), it moves just far enough out of alignment that the 2nd octave dies.
Suggesion: try blu-tacking a guitar pick or other piece of plastic to the front of the blade, and see if that helps. It should thicken the blade enough it’ll stay in alignment when warm.
Best wishes,
–James
http://www.flutesite.com