Techincally, the (standard) Harley does fire during the same crank rotation when one considers that there is only 305* between the F&R power strokes. The common misconception is the 45* firing sequence.

As for the XR750 45*- 675* sequence? I have read that the long pause between the power cycles aids "hookup" on dirt tracks allowing the rear tire to recover grip between power pulses., much like a large single cylinder.

As well as the induction benefits, an added beneifit of the dual carbs is that it allowed the exhaust ports on both cylinders to be located forward to help somewhat in the rear cylinder cooling. The rearward location of the rear exhaust port contributes emmensely to the rear cylinder running hotter than the front.

Back to Saitos.

The firing sequence of the Saito 90* "V" twin in the clip should be 270*- 450*. The alternative would be 90*- 630*.