1998-2001 Honda Fourtrax Foreman TRX450S, TRX450ES Factory Service Manual, Page 143Get this manual
CYLI NO'ER HEADCYLINDERPISTON Inspect the pisto for wear or damageM easure the diameter of the piston at 10 mm(O.4 in) from th bottom and 90 degrees 'tile pi stOl) pi holeSERV.CE iM IT: 89.90 mm f3,S39 inl
Measure the piston
SERVICE LIMIT: 19.08 mm (0.751 in)