[BlackBall]

I would not advise trying to port your own head. Places that do it machine them out and have flow-benches. If you have some dremel skills, you can go in and clean up some rough edges etc, but I wouldnt try and full on port it yourself.

 

[BlackBall]

PRC ports the head as much as possible and uses flow benches to test. And I beleive it only costs $80 for an xr50 head.

 

[BlackBall]

Its for the stock head. I am not sure what they do exactly. I wouldnt think for $80 they put bigger valves in, I beleive they change the size and shape of the tunnels. I do not know much about porting I was just stating the price I had heard from someone.