ATV 250 Service Manual page 176

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If out of specification, rebore or replace the
cylinder and piston (Replace in a set)
.Measure the diameter "P"of piston lower part
with micrometer, is the measuring position
is 4mm away from piston bottom(0.16 in)
Pistor lower part diameter "P"
Standard 70.92~70.97mm(2.792~2.794 in)
If out of specification. replace the piston and
piston ring as a set at the same time.
.Calculate the mating cylinder clearance with
the following formula
Mating cylinder clearance= "C"- "P"
Inner diameter of cylinder"C"
Pistion lower part diameter "P"
Mating cylinde clearance: 0.04~0.06mm
(0.0016~0.0024 in)
Limit:
0.15mm(0.0059 in)
.If out of specification, rebore or replace the
cylinder, and replace the piston and piston ring
as a set at the same time
15.Piston ring and piston pin
Piston ring
1)Measure
.Clearance between piston ring and ring groove
.Use feeler gauge ¢Ù
If out of specification, replace piston and a set
of ring
Caution
First clean the carbon deposits inside the pistion
ring and ring groove, followed by measuring
the clearance between piston ring and ring
groove.