1998-2004 Honda Foreman 450 factory service manual, Page 153Get this manual
CYLINDER HEADCYLINDERPISTON Inspect the piston for wear or damageMeasure the diameter of the piston at 10 mm (O.4 in) from the bottom and 90 degrees to the piston pin holeSERVICE LIMIT: 89.90 mm (3.539 in)
Measure the piston pin boreSERVICE LIMIT: 19.08 mm (0.751 in)