New to this site. This is actually my first post and can't be happier to of found this site. I am in the hunt for a new bike and my neibour has a 2003 YZ450 for sale for $2000. He had the motor gone through, with hight comp piston, new cams, new exhaust. Not sure if he jetted it or not, but when I rode it last night, it isn't smooth. There is allot of ride time on this set up, so it's not like this is all brand new. 1) Idel is real hi, so I screwed the idel screw in all the way, but still hi. 2) Under power, the bike kinda pulsates, and isn't smooth. 3) Back-fires when you let off the throttle and one when kicking to start. Are these things all an indication of bad jetting, or could there be something wrong with the motor re-build? Thanks for any help.