this comes up a lot, the boots crack and look like they are leaking, but unless you have a vacuum leak its probably ok
there is a thread on this somewhere with a photo of the boot sawed down the middle. Im not sure how to find it at the moment.
The ends are alum where it bolts to the head and the carbs, and the middle is plastic all the way thru. There may be a different type of plastic on the inside that does not crack.
So short answer: spray the boots with brake cleaner or hold an un-lit propane torch in the area while the bike is idling. If the RMPs change (usually faster) then you have a vacuum leak. If the idle stays the same you have carb boots with a nice patina crackle pattern, and nothing to worry about.
BTW: usually people post after the fact "My carb boots were all cracked so I bought new ones, took the carbs off and replaced them" and they never verified if there was a vacuum leak or not.
Last edited by KCW; 05-09-2019 at 08:23 AM.