VALVE CLEARANCE 101:  What all 4-stroke motocross / dirt bikes need to have checked.  Valve cam clearance is critical for top power, and valve wear.  Catch and stop permanent valve and head damage on your 4-stroke.  You need to keep valve clearance in specs.  If your valve clearance completely tightens (valve is then hitting the valve seats on the head, and your valve is already wrecked and your seat is to).  Your intake valves will tighten the most and need to be maintained.  A bad sign is your bike won't start, push starting needed, or very hard starting. Don't wait til this happens and you get $400-$500 in head/valve damage and two weeks down time!  Maintain valve clearance before valves ever completely closes- (cannot get the smallest (.0015) feeler gauge under cam).  Check, re-shim when needed to get in spec, and NEVER LET CLEARANCE COMPLETELY CLOSE!!!  Your bike will run at it's best power and you will save a lot of $$$ and time.  All you need is this feeler gauge to get started.