Re: gross jets or not?
I put in a set of Grose jets during a carb rebuild 12-13 years ago and never had a problem with them. Shortly after the install the jets became "unavailable" ... I don't know the history.
When I went to a triple ZS set-up a std needle valve was used in the third carb. It and a replacement leaked through when the gas tank was full.
Grose jets were then available again from 1 of the big 3. I got 2, one for a spare, I thought. The newer ones look slightly different than the original, but are functionally the same. The first one had a problem right out of the package - the big ball lodged in the retainer and finger pressure wouldn't get it to release! It would have stuck open if installed. A good rap on a table freed it up, but it only lodged again when inverted. Seems the retainer hole was just a bit too large - the ball almost fell out, but jammed instead. That one got sent back. The other has worked perfectly.
A big advantage of grose jets is that if you do get some crap in them and they won't close, they can usually be cleaned with a dental pick & compressed air. Then good as new.
BB