Bought an XS650 front hub that turned out to be narrower than the XS650 hub. Same axle size because i bought it with an Axle and speedo drive that fitted another XS650 front hub i have.
Did a lot of research and asked questions on here, (no help from the site), and the only bike i found it could come from was the XS360. problem with that was the XS360 is a 77/78 year and the hubs came with a plasic cover for the side that didn't have the rotor on it, the hub i bought had the early chrome plate that is used on the 74-76 Xs650 hubs.
All holes, (rotor), will swap in XS650 rotors. early XS250's had mag wheels, later XS400 had mag wheels, (to my knowledge), XS500 has a different size bearing for the axle but a bearing (ID), to suit an XS650 axle, can be put in if i recall, (5twins will be able to confirm as he knows these inside out), but the Small hub i have the OD of the hub bearing is the same as the XS650.
Overall the small hub, (XS360??), is 6mm narrower than the XS650/XS750 front hub.
What does this have to do with the guard...........If the hub is an XS360 then the forks on the XS360 are 6mm narrower than the XS650.