Hi Stephen, I'll let others respond regarding how much to take off. However, I would think that matching manifolds and gaskets to the ports, without removing much material would be beneficial. I can see that the ports are not symmetrical. You won't be doing much, but you would be reducing turbulence and increasing flow. The former is good for a combustion chamber, but slow in the passages into and out of the chamber. I wouldn't much call this porting but just cleaning up casting flash and that sort of thing. Like blue printing, matching weights of pistons and rods, always gave a bit more power, without actually changing engine dynamics. Sort of like Vincent motors, the Rapide was not as balanced as the Shadow though their tuning was not very different. Better balance means less friction, more power and ultimately more longevity at high RPM. Its what made my Aermacchi motor spin to 9,000 without sending out the rod.

Location: Seattle, Washington, USA