I was just wondering what exactly happens when you send a 250R motor to a company to have it ported & polished? What specifically do they do to the engine? Also, what improvements does it do to the engine as far as low-end, midrange, and top-end? Any help that can be given is appreciated.

 

2 stroke porting has more to do with altering port timing than what is traditionally thought of as "porting & polishing".

On a 2 stroke, altering the port timing is just like changing the cam in a 4 stroke. It alters the intake and exhaust timing and an experienced tuner can put the power right where you want it, make it broad or "peaky".

Sometimes the ports are reshaped and/or hogged out to compliment changes in port timing and other mods.