1986-1989 Honda TRX250 FourTrax 250R Service Manual, Page 18Get this manual
GENERAL INFORMATION
OPTIONAL PARTS LIST
ITEM ENGINE Oversize pistons
Piston manufacturing tolerance mm (in) 66.20-66.22 (2.606-2.607) 66 .4566.4 (2.616-2.617)
REMARKS .25 mm, 0.50 mm (2 sizes) The cylinder must be rebored, and an oversize piston and piston rings itted if worn or seizedUse the correct oversize piston rings with an oversize pistonOversize rings 0.25 mm, 0.50 mm (2 sizes) NOTE: After reboring, remove all burrs from each port edge and chamber as indicated belowCYLINDER After '87: SIDE Exhaust port bottom end
Oversize
0.25 mm (0 .01 in) 0.50 mm (0.02 in)
Piston oversize
Cylinder .0 Service limit mm (in) 66.32 (2.611) 66.57 (2.621)
1.0 mm (0 .04 in)-'IL._ _
(0.01 in) 50 mm (0.02 in)
(0.06 in) CYLINDER SIDE 0.5 mm