I can't say I've ever heard of anyone doing this..
Kinda makes you wonder why?? Since boiling water would do little or nothing to remove hard dry varnish in an old carb..maybe soften it a bit.
The commercial carb cleaners would do a much better job..
If you have a really fouled carb a barrel of good old fashion carb soak is the thing..smell like hell, but sure does work!!
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)