Wanted to get the R90S out for a ride this year and found that the inlet seat on the left side Dellorto was leaking. Ordered one--they come as a set, with needle and screw-in seat. The OEM seat is stuck. It will not some loose using a 1/4" drive 9mm six point socket. I only tried this with the screw handle type driver, not a ratchet. I'm pretty sure any efforts with a ratchet will result in a twist-off. I am soaking it with Kroil while I contemplate options, like maybe a heat/freeze cycle. Oh-- the new needle will not interchange with the old seat, as the new needle is hex cross section vs square cross section for the OEM and is too big to fit.