S&S Cycle Sidewinder 3 5/8 Big Bore Cylinders for 1936–1999 Big Twins - Manual (Page 16)

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Pistons which do not run true in cylinder bores may cause excessive connecting rod side thrusting. This in turn may lead to premature
ring, piston, connecting rod and rod bearing wear and eventual failure of these parts.
Checking Pin Procedure
A. Insert checking pin into wristpin hole. Place strips of paper between checking pin and crankcase cylinder gasket surface and apply slight
downward pressure to wristpin end of rod by rotating flywheels. Pull papers out slowly. Drag on papers should be equal.
B. Rotate flywheels in opposite direction until checking pin contacts cylinder gasket surface again. Repeat procedure to rod again. If drag on
papers is equal no bending is required. If one paper is loose, use rod bending tool to tweak rod in direction of loose paper and recheck.
See Picture 12, below left.
C. Repeat checking and bending procedure for other rod.
Visual Procedure
A. Install pistons on rods without rings or wristpin clips. Bolt cylinders with gaskets in place.
B. Move piston tight towards camside of engine.
C. Turn engine over in normal direction of travel 2 or 3 revolutions and observe piston during process.
D. Move piston towards driveside of engine and repeat Step C. If inaccuracies are present due to machining variations in cases, cylinders or
pistons, top land of piston deck will appear closer to cylinder wall at one point around circumference. This means that piston is cocked in
cylinder bore and can be corrected by bending rod in opposite direction. Figure 6, above right, shows an exaggerated side view of this
condition.
E. Repeat Steps B to D for other cylinder.
CAUTION
Figure 5
Picture 12 Figure 6