On the bell of the carb, not where the carb meets the block. I should have posted a photo with it.



I have been using CA glue on mine and so far I have not had one leak. I know of other people who run a bead of sealer around it, but sealer is easy to tear. I had recently seen a thin bead of JB Weld used. What happens is the aluminum bell expands at a different rate than the plastic carb body. That allows an air leak that only appears as the carb becomes heat soaked. Not all of them did it. I have more Piccos than any fool should have. This is an issue that sometimes requires attention.



There is your bead of silicone for the carb base.



There is your backing plate seal.



Back to the carb, the bell at the other end may need sealed too. It should be covered by the silicone boot, but they can suck air at the aluminum to plastic connection for the same reason, different swelling rates.

You may also get one that stops idling down when it gets heat soaked. The slide to carb bore fit can be so tight that the slide will get heat soaked and stick in the bore. I had one that was so bad about it, you could not push it shut with your thumb, until it cooled off, then it worked normally. I use toothpaste and apply it to the slide. I chuck the slide up in my drill and run it in and out, using the toothpaste as a seating compound, similar to the old valve lapping compound in engines. It is pretty easy to clean the toothpaste out with hot water and Q tips.

Finally, they cut the slot for the idle screw to very close tolerances. If your carb sticks, back that idle screw way out and see if it still sticks, if not, the slide is swelling and trapping the tip of the idle screw as it gets heat soaked. I chuck the idle screw up in a drill and spin it on a fingernail polishing stick or very fine sand paper. You do not need to remove much, I have also used a fingernail file with my drill.

I agree, do not weld or glue your carb to the block. If you read my previous post, I think that was fairly clear, now you have photos too. Bud

Edited as I see it was not my tip you replied to, but the guy has the right idea. I think you read something else into it. I try to catch as many of these threads as possible as a few minutes attention can save you hours of frustration. The Picco is a super engine, they just have a few areas to watch. Bud