i thought this might be handy to have over here
according to these charts 77-81 xs400's have 33mm stansions
82-83's have 35mm stansions
Fork Diameter Make Model and Year
27 Honda MB5 (82)
27 Honda CR-60R (83)
27 Honda XR-70R (97-03)
27 Honda XL-70K (74-76), XL-75 (77-79), XR-75 (72- 74-78)...