Nut M7 3,5 mm flat for gearbox cover plate Lambretta of all series 1-3 Lambrettas (only exception is the TV 175 series 1).
The gearbox cover plate must be fixed with all six nuts. The tightening torque is 14 - 17 Nm.
If a thread is defective, you have to have it repaired. All practical attempts with five nuts or less have failed miserably.
AI-translation/sub>