bluesman

In "Tickling noise" tread I saw link to Mototune....and there I found this article on porting.
Thou I really do not like shouting style of this article, I want to think about matter...very controversial actually...

Anyway - what do you think? Does he have a point?

http://www.mototuneusa.com/think_fast.htm

RymerC

it's widely accepted that the valve throat area should be 85%(off the top of my head???) of the valve diameter. I don't know what the stock ports on the superhawk head look like, but there's almost ALWAYS room for improvement.

Also, changing the shape and volume of the ports will shift the powerband of the engine somewhat. So hogging the snot out of the ports may help if you're pushing 25psi through it at 12,000RPM, but not N/A at 3000.

RCVTR

I've read the articles and believe a lot of what is presented there. He is working with 600s in the article. Fattening up the midrange torque on a 600 could be very beneficial in the real world, likely at the expense of some top end horsepower. Peak horsepower sells motorcycles. Flat torque curves and linear horsepower wins races. Linear HP makes the connection of the brain with the rear traction more natural. I believe that allows the rider to ride harder and closer to the limit.

Look at the torque curve on the VTR engine. It is horizontal from about 5500 to 8500 rpm. How are you going to improve on that? Some mild porting work improves the top end slightly, without hurting the midrange, but I don't change the profile much, except to flatten the floor slightly by putting a smaller radius at the bottom corners. Leaving the surface roughness on the floor until you finish the sides will help prevent changing the floor curvature. Then smooth the floor last. Make sense?