American Motorcycle Dealer AMD 172 November 2013 | Page 53

S&S Cycle three-piece
flywheels
S&S Cycle has identified the need for stronger
flywheels in tuned engines. A particular problem with
tuned stock Harley-Davidson motors can be that the
stock flywheels shift out of true.
To deal with this issue S&S Cycle is now producing
three-piece flywheel assemblies with integral
sprocket and pinion shafts, an all new connecting rod
and crankpin. The company states that the new
assemblies are a vast improvement over stock, and
are even superior to its own flywheels produced
previously.
The heat-treated 4140 material is claimed to be
not only harder than stock but also 114 percent
stronger. Due to the use of this harder material the
need for a thrust washer is eliminated.

In addition, a larger 1.671in diameter crankpin
with a five percent increased cross-sectional area for
increased crank-pin clamping force is employed, as
is an integral mainshaft to eliminate two potential
points of weakness. Reduced mainshaft deflection at
high rpm produces less vibration and reduced piston
and rod side-thrusting, which prevents oil pump
damage. Less vibration is also achieved through
consistent balance and precision-machining to
produce truer flywheels, and they are trued to within
.0005in and the TIR rod bearings have 20 rollers
instead of the 18 used as stock.
S&S Cycle is making the three-piece flywheel to fit
‘99-’06 Harley-Davidson Big Twins (balanced and
unbalanced models) and S&S T-Series Engine and
Hot Set Up Kit replacement flywheels, and a second
version for use in ‘07-’13 H-D Big Twins (balanced
and