I've just had the valve guides in a Gen II cylinder head replaced.
The old guides in the head had been pressed down then ground to match the contours of the ports.
This time the machinist left the guides protruding in to the ports.
He says that it really doesn't make much difference in air flow to not contour them to the port but makes for better accuracy when cutting the seats on the next valve job. The second part makes sense.
Frank has been doing heads for 25+ years but isn't a Hayabusa guy. He has a flow bench and builds lots of R6 heads for roadrace guys and has built some bad-ass CR450F engines where he does all the porting etc.
He does gorgeous work and I'm really happy with his workmanship. Just wondering for myself if there is a worthwhile difference in contouring the guides to the port in a Hayabusa.
Thank you, Mike