The V4 are asymmetrical whereas the I-4s have equal intervals. The firing order with a flatplane V8 allows for perfect balance between banks - each subsequent firing cylinder being on alternating left and right banks. It's no so much the firing order, but the interval between firings. More: I don't understand why NorCal has a bug up his ass about this. This would lead to torsion issues (hence their vibration issues with the exhaust headers), and put unnecessary work on the oil system. Don't get me wrong, I love my V4s!, but certain engines just have a great sound, one that has stuck in my memory for years was a 427 Ford at the drag races, don't what was different about, but man it sounded great. The current firing order loads the same crank pin just 90 apart, for example 1-5 would fire opposite bank, but same crank pin. Cross planes with aluminum or titanium rods can hit 8500. With the odd cadence and firing orders of the V-4s they have their own unique sound. The crankshafts have an odd firing order (less efficient) and are heavier. Exhaust pulses are evenly timed and create a more pure musical frequency. What you need to know is that the flat-plane crank changes a V-8s firing order so that the two banks of cylinders fire at even intervals relative to each other.

I still don't think sound is as hot as a well tuned I-4 with a pipe. Now I have both the 83 & the 14 with totally different engines and different sounds. To me VF750 never sounded like a 'hot' bike, but it sure pulled like one. When I first got my '83, I got a Vance and Hines 4 into two system. I thought is was a reasonable explanation and at least he took the time and effort to relate it to a musical example.

Flat plane crank firing order