Piston Pin, Bearing; Assembly - Yamaha YTZ250S 1986 Service Manual

2. Holding cylinder towards light, check for
full seating of ring around bore. If not fully
seated, check cylinder. If cylinder is not
out-of-round, replace piston ring.
3. During installation, make sure ring ends
are properly fitted around ring locating pin
in piston groove. Apply liberal coating of
two-stroke oil to ring.
NOTE: ______________________ _
New ring requires break-in. Follow first portion
of new machine break-in procedure.
Piston Pin, Bearing
1. Check the pin for signs of wear. If any
wear is evident, replace pin and bearing.
2. Check the pin and bearing for signs of
heat discoloration. If excessive (heavily
blued), replace both.
3. Check the bearing cage for excessive
wear. Check the rollers for signs of flat
spots. If found, replace pin and bearing.
3-16
Assembly
1. During re-assembly, always use a new
cylinder base gasket.
NOTE: ______________________ _
Be sure to tighten the cylinder head nuts to
specification.
Cylinder nut torque:
35 Nm (3.5 m-kg, 25 ft-Ib)
Cylinder head nut torque:
25 Nm (2.5 m-kg, 18 ft-Ib)
2. During re-assembly, coat the piston skirt
areas liberally with two-stroke oil.
3. Install new piston pin circlips and make
sure they are fully seated within their
grooves.
4. Take care during installation to avoid
damaging the piston skirts against the
crankcase as the cylinder is installed.
NOTE: ______________________ _
The arrow on piston dome must face forward.
5. Add the transmission oil and coolant to
specification.