S&S Cycle Sidewinder 3 5⁄8 Big Bore Cylinders for Harley-Davidson Sportster Models—1986–2003 - Manual (Page 11)

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2. Piston to Flywheel Clearance
a. Perform Steps 1 through 3 in Connecting Rod Clearance (Step A, page 9).
b. Rotate flywheel to position where front piston is closest to flywheel. This is at the bottom of the stroke. See Picture 14, previous
page.
c. Check clearance between piston and flywheel.
NOTE: A minimum of .060" clearance is required between piston skirts and flywheels at the bottom of stroke where pistons are closest to flywheels.
d. If clearance is not sufficient, disassemble cylinder and piston, and carefully file piston skirt until clearance is obtained. Skirt of piston
may also be fly cut on a milling machine to provide clearance.
e. Reassemble and recheck clearance.
f. Repeat procedure for rear piston.
10. Connecting Rod Alignment (All)
NOTES:
• The purpose of this procedure is to correct for machining tolerance discrepancies in components which may lead to pistons not running true in
cylinder bores. While rods may be straight and true, it is sometimes necessary, to bend them to correct for these machining discrepancies. Do not
bend rod by using tool in wristpin hole as this method may distort wristpin bushing. We also feel that using a piston in lieu of a checking pin may
prove inaccurate due to variations in lengths of piston skirts from one side of piston to the other.
• All engines should be checked upon disassembly for incorrect piston alignment. This applies to those which are receiving new pistons as well as
those being completely rebuilt. Observe pistons for wear spots on sides above top compression ring. If one side near wristpin is worn clean while
side opposite is carboned up, then piston was not running straight and true in cylinder bore. Piston will also generally show diagonal wear pattern
on thrust faces of skirts and possibly signs of connecting rod to wristpin boss contact inside piston.
• We feel that not enough emphasis is given to checking piston alignment in cylinder bore. Proper piston alignment means connecting rods will
thrust to sides less minimizing added stress on pistons, rings, rod bearings, and other related parts.
• S&S® Rod Checking Pin, part 53-0002, was designed to help perform this procedure. It may also be necessary, to fabricate a rod bending tool as
illustrated in Figure 3, below.
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.
A. Install flywheels in crankcases per Harley-Davidson® factory procedures. After flywheel assembly is installed in crankcases, rods must be
checked for straightness.
NOTE: Pinion Shafts included in all S&S flywheels kits for Evolution® Sportster® models and assemblies are of the 1987 type. This means that 1986
crankcases must be converted to use the 1987 and later style caged roller pinion main bearing assembly, and that 1986–1987 style pinion gear
and oil pump drive gears must be used in 1988 and later engines. See Step 6.
Figure 3
CAUTION