AD Boivin SH-MAN-2007, Shop Manual

Page: 187 / 251

ENGINE (CYLINDERS / HEAD / BASE / EXHAUST) 7 - 33
RING/PISTON GROOVE CLEARANCE
Using a feeler gauge check clearance between
rectangular ring and groove. Replace piston if clearance
exceeds specified tolerance. Refer to
Chapter 15 – Dimensions
and Tolerances.
RING END GAP
Position ring half-way between transfer ports and intake port.
● NOTICE:
In order to correctly position the ring in the cylinder, use piston
as a pusher.
Using a feeler gauge, check ring end gap. Replace ring if gap
exceeds specified tolerance. Refer to
Chapter 15 – Dimensions
and Tolerances.
1. Transfer port
2. Intake port
CRANKSHAFT DEFLECTION
Crankshaft deflection is measured with a dial indicator.
Measuring (in crankcase)
First, check deflection with crankshaft in crankcase. If deflection
exceeds the specified tolerance, recheck deflection using V-
shaped blocks to determine the defective part(s). See below.
Measuring (on bench)
Once engine is disassembled, check crankshaft deflection on V-
shaped blocks. If deflection exceeds the specified tolerance, it
can be worn bearings or a bent crankshaft. Remove crankshaft
bearings and check deflection again on V-shaped blocks
to determine the defective part(s). See measurement A in
following illustration.
1. Measure at mid point between the key and the first thread
A. 3 mm (1/8 in)