I do straighten the port walls a bit when I port the Homeys, but I don't widen the port where it enters the cylinder much. Just a little to blend everything in well. The main improvement comes from getting the timing up to around 150 degrees for operation below 8000 rpms, and 160 or so for operation above 8000. The timing is important and you will see good results from going to 150 degrees if your carb and muffler are up to the task. Keeping the port fairly close to stock size keeps the flow velocity up and the timing does the rest in this case.

Stones don't work very well on aluminum as they clog up almost instantly. I use carbide cutters. Once again, be sure to chamfer any port edge you have touched, and be sure you go slow with your porting. A small amount makes a pretty big change, as it makes the port open earlier, and also close later. So you effectively get a "double" timing increase for each increment you grind out. I have a tiny little flex light that I insert into the spark plug hole. Makes it real easy to see exactly when the exhaust port opens and closes while looking into the port.

AV8TOR

P.S. If you want to pm me your e-mail, I will send you a nice degree wheel that you can print out...