Lord knows why BMW felt the need to use weird headlight sizes. Standard circular automotive headlights were 7" or 5.75". BMW used 8" on the bigger bikes and something like 6.5" on the R65/45. Honda used/uses the same size headlight as the R65/45 on their CB250T, CB400T, CB250N, CB400N, Superhawk, whatever they were called in your part of the world, right through to their current bikes still using essentially the same motor. Affordable aftermarket headlights for the Honda will fit the BMW too.