34
ST SERIES
ENGINE PARTS CHECK
❱❘ Cylinder – piston wear condition
• To determinate cylinder wear, measure cylinder bore with a dial bore gauge, about 10 mm from
the cylinder deck. Make a cross-measurement in order to check ovalization.
125cc 250cc 300cc
A B A B A B
Ø Piston 53,96
53,97
72,76
72,77
78,95
78,96
Ø Cylinder 53,975
53,985
72,79
72,816
79
79,016
Clearance 0,015
0,020
0,04
0,046
0,05
0,056
❱❘ Reeds valve, intake boot
•
Over time, the carbon reeds gradually lose
their elasticity, which causes a loss of power.
•
Replace used or frayed reeds, taking care of
applying threadlocker on the stoppers screws.
•
Check intake boot condition, especially
looking for cracks.
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