Yup, that's very, very common.Suzukidave wrote:The needles and needle jets sure were worn .. needing replacement
The issue is the plastic slide guide, as I said.
Here's the pisser... they are unobtanium as a separate part from Mikuni

Otherwise, you'd just replace the guides at the same time as the needles and needle jets and you'd be good for another five years or so, instead of only approx 5000km, which is how long it takes for the needles to rattle themselves to oblivion in the jets with the slides banging about all over the place.
If there's anyone out there willing to re-manufacture the guides in a harder plastic to prevent wear, they'd be able to rake it in from the vast numbers of GSX-R owners with knackered carbs!
You haven't got a 3D printer handy at all?