sand down ALL motor mounting points and ANY places where coils mount/ground. if you dont, you won't have any continuity and you will have no spark at the plug. you will find that sandpaper wont cut it very well. get a grinding bit for a drill or a die grinder. sandpaper will take you all day and half the night just to make a dent in it. also, invest in a tap and die kit. you will need to tap out ALL the holes in the frame just to be able to get any bolts to go in at all.
Hey, treejumper.....didja ever get that busted crankcase on ur YZ fixed yet???