This has probably been asked before but I never have any success with the forum search tools…
What RPM do we consider to be the maximum for sustained motorway cruising on these bikes?
On a 15T front sprocket, 70MPH (indicated) is 4600ish and 80 is just under 5000 but It’s all starting to feel a bit fraught at 5000 to be honest.
The redline looks like 6750 (is that right) and I seem to remember an old adage about not running an engine at more than 2/3 maximum RPM for any length of time. 2/3 of 6750 is 4499 RPM so that should mean that 70 MPH is fine and you can take a blast up to 80MPH for getting round stuff.
I always try to feel and hear what an engine is telling me and mine seem very happy at 4000 to 4800, after which the vibes increase suddenly (which I take as a sign to calm it down), also peak torque is 4500ish so that means the engine is at its most efficient at that speed.
BTW I went to France last year at 70MPH the whole way, could have gone faster (I was riding with bigger bikes) but I set the speed and they had to lump it. The FX did 800 miles on that trip and seemed to love it.