Mk6 Bultaco Manual says:
Clutch dry 300ml, or refill 250ml of SAE 30
Gearbox dry 600ml, or refill 500ml of SAE90 (tilt bike over to drain out most oil)
Mk10 Bultaco Manual says:
Clutch dry 300ml, or refill 250ml of SAE 30
Gearbox dry and also refill, 600ml of SAE140 (tilt bike over to drain out most oil)