me and cordesh had this same prob after our rebuilds. mine was with the stroker crank and if i remember his was stock crank. it turned out to be the crank seal, the dealer gave wrong one. the inside diameter of the seal was to big, dont remember exact numbers but i think mine was 34 inside and i was suppose to be 30. mine would through about a half quart of the engine oil in the airbox.I have a 05 450r with a 3mm stroke crank, stock bore blowing oil out the crankcase breather bad. The motor is a new build with the second top end same problem. Any ideals? Bad oil pump maybe or something stopped up![/b]
also heard of bad rings, cracked piston, misaligned rings as some other reasons for this.
good luck and hope its and easy fix