some of those sites will botch the job (porting) --and still plop it in the box and sell it to you. because it will still run. but you,.. the new guy,... have no idea that the guy f***ed up,....all you know is that your reed valve is giving you more power than your other, bare bones motor and youre happy. you gotta watch these people.
someday in the future you will try it yourself,..and THEN you will understand a botch job from real port work.
IMO being able to successfully port a motor, and see a significant gain,... means you have left the ranks of boys and have become a master at these motors. that is the moment. I know,... because im STILL afraid to do it. LOL!!!
---ALL of those gains,... resulting from ALLL of that effort and $$$,.... mean nothing when your wrist pin bearing comes apart and destroys your motor. IMO its all a bunch of hooey. get a cheapo stock motor with a NT carb,.. set the needle right,... and keep the rpms low and varied. youll get 90 percent of the power,.. for 5x as long. ppl do this stuff,.....and then think they now have a suzuki RM125motor,... and proceed to scream the rpm's. wrist pin bearings don't like that. and the sad part is: if it isn't your wrist pin bearing that lets go,... something else surely will. these things just cant take a beating. and all those do-dads will make you THINK you can beat the hell out of it.
you CANT.