I also did my first valve check at 400 miles and everything was in spec. The bike is a dream to work. It's super easy to get the valve cover off and work on the valves. Great design and lots of maneuver room.
While I was at it I added a crank case breather hose so I don't get any oil in the airbox.
Additionally I installed a CRF450X mud-flap since it is a rigid piece versus the floppy rubber OEM Husky one.
The fit is perfect and requires only relocating the left hole.
I also trimmed a bit of the mud-flap to allow it to sit flush w/ the swing arm. There is a section of the upper chain guide which interferes whit the mud flap.
I feel like the OEM chain is too short and should be a couple of links longer to allow for more clearance between the tire and the swing arm. It's pretty tight in there and there is tons of adjustment room to the rear.
Following an inmates suggestion I moved the rear tug strap from the side panel bolts to the rear frame bolt: