How clean is clean ? Mystery blockage !

I've recently started rebuilding another set of carbs, these I believe are '81's. The return springs on the throttle-shafts are missing a "hook-bend" which are on the '79's and '80's that I've previously worked on. OR, maybe just a different "spring" supplier OR maybe it was determined the hook-bend wasn't necessary. - Doesn't matter. Just another piece of almost useless info ! ( Or is it? )

After giving these carbs a preliminary cleaning a "function" inspection determined that the air-bleed on one of the bores and on two individual carbs was blocked. The "function" inspection is nothing more than blowing air through the various passages to ensure they're clear. A visual inspection with a high intensity light looking into these air-intakes for these bleeds discovered these strange objects. They blew-out by applying air-pressure "backwards" through the appropriate port elsewhere. What came out are pictured below. My first impression was that they were from residual sealant applied to the metering jets, (deep in the passage) during the assembly of the carbs. Upon a closer look it was obvious that the ends were completely formed closed (directly over the metering jet). This would have made a successful flow-testing(?) of these carbs at the Mikuni factory impossible. Presumably each bike would have been run through some tests to ensure that they would indeed run, before shipping from the Kawasaki plant. The bike would not have run correctly.

Due to their thin, paper-like feel and their color I believe this is the best answer. I think they are "pupae" casings from some insect. Given there was every indication from the condition of the carbs that the bike had been run (and likely put permanently behind the woodshed without an air-filter), it makes more sense than a factory mistake.

I thought I had seen it all when rebuilding these carbs but apparently not so. This is a new one ! The only reason I found this blockage is because I've rebuilt enough sets of carbs to know, "NEVER take anything for granted" and "It's easier to do it thoroughly and correctly the first time than it is to have to remove them and do it all over again" ! Lacquer-thinner obviously did not dissolve these !

Note: I placed the "whatever it is" partially into the idle-air supply port for description clarification. When discovered they were all the way in and up against the air metering jet deep inside the port itself.

Yes, almost certainly insect pupae casings. More common in carburetor and other mechanical parts than you would believe.

Now we all know that if anybody could get the "bugs out" of a set of carbs it would be you!! :lol:

Wildlife does seem to be attracted to old 1300's

Would moth balls help to solve the problem :whistle:

Its a shame as that air cleaner looks like it should be put in a musuem :lol: