Well, my Jerry Freeman red top gen whistle (brass) head cracked, key of “D” . I wrapped it with silver duct tape but its not the same now, sad to say. 
It was a great sounding whistle too!
The ones i own that have cracked haven’t changed a bit sound-wise.. (they have all cracked in the ‘sleeve’ that goes on the tube)
Same with mine! But it went all the way to the window. It still plays but my A note is now funky in a bad way.
Have you spoke to Jerry?
I’d bet good money that he will make it right.
I’d advise anyone to do the same.
@ Maki…Not yet! I did however re-wrap the mouthpiece with black gorilla tape from home depot. Its back to being great again…for how long? who knows? A $3.50 fix tho…
As Maki noted, Jerry fixes these at no cost.
They are plastic heads so they do break from time to time. I usually wrap mine with either thread or fishing line as you would wrap a fishing rod guide. Then paint a couple of coats of clear nail polish over them.
send him an email.
ecohawk
In one of Jerry’s post he tells you how he does the fix on them…http://www.ropeworks.biz/reader/whipping.pdf I used whipping method # 2 and fingernail polish(two coats). This works really well and does not take long at all. Now, mine didn’t turn out as pretty as jerry’s for my first try BUT it does work and will last a long time. Cost to fix my whistle was a little more than $2.00 at the .99 cent store.
Must be the hot weather here in Arizona cause my other red top gen D brass(un-tweaked)cracked today. Glad I learned how to repair this!
Were you leaving them in a hot car, by chance?
One of my non-tweaked generation Bb’s got a tiny crack around where the head adheres to the tube. I put a bit of tape over it, continue to leave it in my car (during blizzards and heat-waves, for over a year since the crack), and the crack has not expanded at all. The whistle sounds the same as it always has. I do assume it’s hotter in arizona, though.
Are you sure nothing might have happened that could have caused the crack?
Nope, not left in a hot car. I went to bed and when, I started my practice session the next day that’s when, i saw the crack on the sleeve of the mouthpiece. From what people have said on this forum the generation whistles all seem to crack in the same place. Now, i also have a few blue top generation whistles and they have not cracked!
In my experience Generation heads only crack after suffering some form of maltreatment.
Some people’s whistling can be described as maltreatment. 
Thanks for the insult!
Nothing personal.
How do you store your whistles when they aren’t being played? And are they transported often, or just kept at home?
If I recall correctly, this has been much more pronounced lately.
Something about a new plastic formula used by Gen.
kept at home in a cardboard mail tube. The only time I travel with them is to a recording studio in the city where I live. I don’t do that very often. They should not have cracked BUT the weather here is brutal! As in HOT! Temp in my apartment is between 82-86 degrees and I have evaporative Cooling
Hmm. That is a mystery. I don’t think that the temperature would cause that sort of cracking alone, without a manufacturing defect or some accidental damage. I take it that you aren’t cleaning the whistles with polish or anything? Do you loosen the head with boiling water when you buy the whistles? I wonder if the heads are on too tight, which might cause stress cracking. If the whistles are stored in the cardboard tube, then it can’t be sunlight weakening the polymer.
One whistle is a Jerry Freeman Gen tweaked the other is a stock Gen both have red tops and brass body. The stock one is a tight fit tho. I did the hot water trick on the stock one to make it tune-able. The stock Gen is a killer sounding whistle too. Like i stated in an earlier post…I have a few blue top gens and no cracking with them…knock on wood! Tis very strange to say the least…maybe it doesn’t take much to crack them is what i’m starting to think…Hmm? PS: To answer the rest of your question…No, I don’t use polish of any kind on them. I would be curious to find out if anybody else has had this problem recently (within the past three or four years)with generation red top whistles(brass body).
Update:
Well, I had another whistle - head crack and this time its a gen blue top D. Must be when I take them out and put em back in the mailing tube. 
could you post a pic?