Last summer I big bored my yz and from Kustom Kraft the instructions said (the best I remember)to start and let the engine warm up(no reving) ride in a high gear(4th) at part(consistitly) throttle for 5-10 minutes(no full throttle pulls),Stop let engine cool completely and do over about 5 to 7 times,You mush resist the urge to romp on it,What this is doing is letting the piston and rings get use to the bore by expanding and contracting from the heating and cooling cycles! After the big bore kit I had to lean my jetting out .kep fouling plugs!!