RH4 and RH10 Heads

What was the logic behind changing back to the 32mm ports in '75? Anyone know?

More top end? Port floors in the RH4 makes the 32mm port make a lot of sense. I am more bothered by the larger valve guides from the 750 to the 850.

The low crankshaft balance factor in a normal Commando probably precludes more top end. More port vacuum improves midrange performance. One can work either with or against the other depending on how you intend to use and gear the motorcycle. I usually try to get more torque and use high gearing with close ratio gears. But that would not be good in a road bike. My rev limit is 7000 RPM. However 'self-praise is no recommendation'.

My guess would be to reclaim some of the power lost by the emissions control measures?