1989 Honda FL400R Pilot Service Manual, Page 73Get this manual
CYLINDER HEADCYLINDERPISTON CYLINDER AND PISTON SELECTION The cylinder and piston are select fittedSelect new piston andor cylinder as follows:
Piston selection Record the ODcode on the piston headNOTE
A cylinder and piston with the same code must be usedRefer to the code on the cylinder if you cannot identify the code on the piston headUse new piston with the same ODcode as the old one
Cylinder selection Record the cylinder IDcode located right side of the reed
valve base
Use new cylinder with the same I.Dcode as the old oneCylinder and piston selection Use new cylinder and piston with the same IDand ODcodes when replacing cylinders and pistons togetherCYLINDER I.DCODE PISTON O.DCODE