S&S Worldwide Motorcycle Accessories - Manual (Page 9)

2. Piston to Flywheel Clearance
a.
Perform Steps 1 through 3 in Connecting Rod
Clearance (Step A).
b. Rotate flywheel to position where front
piston is closest to flywheel. This is at the
bottom of the stroke. See Picture 14.
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.
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.
B. Checking Pin Procedure
1.
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.
See Picture 15.
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Picture 13 Picture 14
Picture 12
CAUTION