Being of an age when it was accepted that all British motorcycles dripped oil (not leaked), especially those equipped with a Burman gearbox, it was regarded in a similar vein to steam locomotive engineering. It showed that oil was getting to the right place, i.e. the gearchange shaft and as a useful by-product it prevented the exhaust pipe rusting at its most vulnerable spot. However, two of the Burman gearboxes that have come my way were fitted with a leather oil seal/collar. This fitted snugly over the steel bush projecting from the gearbox cover and was sandwiched and compressed slightly by the gear pedal when in place. Whilst not 100% effective it reduced the egress of oil/grease and had no effect on gear changing. I do not know whether these leather seals were an original Burman product or a later addition.