Not much of a chance of it being the hose unless its cracked where the pump fits against it.
Best thing to do is just pull the clutch and see whats going on in there. Should be pretty easy to figure out.
I have ported a 650 for a friend of mine and it turned out pretty good,but its no ported 660 by any means.
Seriously port the head you have if thats what you want to do. If done correctly it will run better than a stock 660.
Terry I am really glad to see you branching out but hate to hear you are getting out of the logging business.
I will be looking forward to the grand opening GTG.