4. Maintenance
USE AND MAINTENANCE MANUAL
CHAPTER 4
MAINTENANCE
XEF 250 - Rev01 / 2020
73
4
A
B
6
1
4
2
3
6
6
7
5
4.7 CYLINDER AND PISTON
Removal
– Remove the head (refer to chapter “4.6 Cylinder head” on
page 71);
– Remove cylinder bolts “1” on the timing chain side, then
remove cylinder “2” from piston “3” and remove it from the
vehicle. Retrieve the centring bushings “4” and remove the
gasket “5”.
– Remove seeger “6”, pin “7” and piston “8” from the
connecting rod.
Before removing the seeger, cover the crankcase
with a clean cloth to prevent it from falling into it.
Do not use a hammer to pull out the pin, in case the
operation is difficult to use a special puller.
Cylinder check
– Remove carbon deposits using a rounded scraper;
Do not use a sharp instrument. Avoid scratching the
aluminum.
– Check the internal surface of the cylinder, if damaged,
grind or replace;
– Measure the cylinder bore in parallel (D1, D3, D5) to and at
right angles to the crankshaft (D2, D4, D6).
– Then, find the average of the measurements.
Bore:
Standard = 77.000 – 77.010mm (3.0315 – 3.0319 in)
Wear limit = 77.60mm (3.0339 in)
If the bore does not comply with the specifications,
re-measure or replace the cylinder, piston and piston
rings all together.
Piston check
– Measure the outside diameter of piston “A” in measuring
position “B” using the micrometer.
Piston diameter:
76.955 – 76.970mm (3.0297 – 3.0303 in)
Measuring point “B” (from the lower side of the
piston skirt): 4.0mm (0.16 in)
If the diameter does not comply with the specifications,
replace the cylinder, piston and segments all together.
– Finally, calculate the clearance between cylinder and piston:
Clearance = Cylinder “C” bore - Piston diameter
Clearance between piston and cylinder:
0.30 – 0.055mm (0.0012 – 0.0022 in)