Have you resolved this yet? If the problem is at very small throttle openings then the needle should have little effect. For most slide type carbs it mostly controls mixture from about quarter throttle up to nearly full throttle, and I gather your bike runs fine in that range. The mixture at smaller openings is mostly controlled by the cutaway and the idle system. Cutaway should be correct as BVF never offered an alternative size, but it could have been modified with a file! The 1982 edition of the parts list shows the idle jet as 35, or 40 “if required”, main jet 135 and needle jet as 70 (without cross-hole). Back in the day many riders found the larger pilot jet gave better running. I did, and also found that correct setting of the float height was important. Good luck!