08-18-2021, 01:55 PM
The 51490-MER-R61 fork seals have been superseded, meaning when supplies run out, the 51490-MKA-D81 will be used. Exact reason unknown, possibly engineering reasons, supplier availability problems, or simply cost.
With Honda, every part has a unique number that is never really changed - it is tied to a blueprint. When a part is obtained from a different supplier, or a material or design spec is changed, the part number is also changed.
Take for example a frame - if one weld is made longer/shorter or a 6mm hole needs to be 7mm, the part number (usually the last 3 numbers) is changed.
That particular fork seal 51490-MKA-D81 is used on almost all the street bikes with 41mm forks, from 300cc to 1300cc.
With Honda, every part has a unique number that is never really changed - it is tied to a blueprint. When a part is obtained from a different supplier, or a material or design spec is changed, the part number is also changed.
Take for example a frame - if one weld is made longer/shorter or a 6mm hole needs to be 7mm, the part number (usually the last 3 numbers) is changed.
That particular fork seal 51490-MKA-D81 is used on almost all the street bikes with 41mm forks, from 300cc to 1300cc.