The infamous turkey gobble

[gspd]

Sounds to me like you might be due for another rear main seal replacement.
There doesn't have to be a visible oil leak, a lot of the gobblers never leak a drop.
Maybe it's hardened and dried up.

[RPGR90s]

I had a spare reed in my kit, when compared to the one in the bike was a bit stiffer. So I installed that and went for a ride. The noise is gone.

Took the bike out Saturday for a 80 mile ride with a neighbor and, just had the most enjoyable time. This time of year in Michigan on a bike is spectacular. Even at 80F, there's a coolness when moving on a bike. And all of the flower aroma's coming into your helmet just make you glad to be alive.

Doesn't hurt that you're doing on a nearly 50 year old perfectly running Airhead either.

Thanks everyone,
RPGR90s

[gspd]

I'm glad it was a simple solution for you!
After years of messing around with a lowsy disc system BMW went to a somewhat better reed system and the gobble noise was 99% gone.
Back in the days of the spring disc type breather we discovered that drilling even the tiniest hole in the disc(s) stopped the gobble noise but too much oil got sucked out of the breather causing really high oil consumption.
Not enough tension on the reed will have the same effect.
I can't recall the specific years and models, but I've seen at least two (brand new) airheads that were burning unacceptable amounts of oil due to faulty (weak?) reed breathers.
If the noise is gone and it's not pumping oil out the breather, you've hit on the right reed tension.

[RPGR90s]

I'm glad it was a simple solution for you!
After years of messing around with a lowsy disc system BMW went to a somewhat better reed system and the gobble noise was 99% gone.
Back in the days of the spring disc type breather we discovered that drilling even the tiniest hole in the disc(s) stopped the gobble noise but too much oil got sucked out of the breather causing really high oil consumption.
Not enough tension on the reed will have the same effect.
I can't recall the specific years and models, but I've seen at least two (brand new) airheads that were burning unacceptable amounts of oil due to faulty (weak?) reed breathers.
If the noise is gone and it's not pumping oil out the breather, you've hit on the right reed tension.

I think that was it. I'll monitor oil consumption, but last weekend's ride saw zero change on the dipstick, so I'm confident.

I realize that Airhead's can have valve train clatter, and turkey gobble noises, but I like quiet machinery, so it's something I like to eliminate if possible.