Here you have one BSA Gearbox main shaft nut, made from solid stainless steel and as a direct replacement for the original. This nut was fitted to a huge range of models that used the 6 spring clutch.

Sometimes referred to as the clutch spring retaining nut.


produced with original 5/8" x 20TPI, correct hex spanner size and cut out from one side that is required for correct fitment!

Part number: 66-3787

Finish: Polished - Tumbler


Each of the parts has had at least 3 hours in our tumbler, this gives them a good finish, please see photos! The finish is not "chrome" or "show finish".


This nut fits any of the following models fitted with a six spring clutch.

A7, A10, B31, B32, B33, B34, M20, M21, M33 and Goldstar (DBD34)

This nut may fit other models but please check your part numbers before ordering.


This item is made using CNC manufacturing in England by CPC Engineering with high-quality stainless steel.

66-3787 - Gearbox Mainshaft Nut (6 spring)

  • Brand: BSA
  • Product Code: 66-3787
  • Availability: In Stock
  • £30.00

  • Ex Tax: £25.00

Tags: Bsa, 66-3787, Gearbox, Main, shaft, Nut, mainshaft, 66, 3787, A7, A10, B31, B32, B33, B34, M20, M21, M33, dbd34, gold, star, goldstar, stainless, steel, uk, england, for, sale, parts, spares, clutch, spring, retaining, cpc, engineering