is this hard to do and does it cost much? i have bought a 77cc cylinder and didnt realise this was neccesary.
Just take it to a good machine shop and tell them what you want, do you want to fit the cylinder or not? What they charge is what they want to do the job properly.
High end 70cc kits and larger displacement kits need the cases milling to fit the larger/wider skirt. Any decent engineers or a car engine shop should be able to do the work. Normally decent kits come with exact instructions on where to mill and how much.
