Just rebuilt the upper on my 2004 yz450f. Hot cams and high compression piston. After a light riding me and a buddy decided the crab should probably be checked and the shims. We rebuilt the carb today and checked the shims. All set to go. Start it up and it's idling and running smoother but there's a knock in the top end... It got quieter as it warmed up but it's still there. An ideas?????