2007-2009 Honda TRX300EX TRX300X service manual, Page 119Get this manual
CYLINDER HEADNALVE Rotate the crankshaft counterclockwise and align the "T" mark on the flywheel with the index notch in the crankcase coverMake sure the piston is at TOC (Top Dead Center) on the compression strokeThis position can be confirmed by checking for slack in the rocker armsIf there is no slack, it is because the piston is moving through the exhaust stroke to TOCRotate the crankshaft one full turn and match up the "T" mark again
Wrap the cylinder head with shop towels to prevent spilling engine oilLoosen the bolts in crisscross pattern in several stepsRemove the head cover bolts and the cylinder head cover