1988-1994 Honda TRX300 Fourtrax, 1988, 1990-1994 TRX300FW Fourtrax Service Manual, Page 82Get this manual
CYLINDER HEADIVALVES INSPECTION CYLINDER HEAD Remove carbon deposits from the combustion chamberCheck the spark plug hole and valve areas for cracksCheck the cylinder head for warpage with straight edge and feeler gaugeSERVICE LIMIT: 0.10 mm (0.004 in)
Check the cam chain guide for excessive wear or damage
VALVE SPRING FREE LENGTH Measure the free length of the inner and outer valve springsSERVICE LIMITS: Inner: 35.3 mm (1.39 in) Outer: 43.8 mm (1.72 in)