S&S Cycle Box 215 Viola, Wis. 54664 - Manual

Service Bulletin - Late Style Evolution Cylinder Studs
Situation: Harley-Davidson early and late style Evolution cylinder studs are so similar in
appearance they are difficult to tell apart. However, even though they look alike they
require very different installation procedures.
Evolution crankcases currently being produced by S&S utilize late style cylinder studs.
The following instructions will detail the differences and alert you to the proper installation
procedure.
Procedures: Late style Evolution cylinder studs H-D #16837-85C for Big Twins and -
#16832-86C for Sportsters have a collar near the bottom end of the stud. (See H-D
Parts and Accessories Bulletin PAB #517 March 22, 1994) This collar rests flush on the
crankcase cylinder deck when the stud is installed in the crankcase. This method of
installation is just the opposite of the way the earlier style cylinder studs are installed,
with the collar near the top of the stud. Although the late style studs may appear to be
early style studs installed upside down, they are different parts and the two styles must
not be confused.
The difference between early and late style studs is in the thread fit and the method
of securing them in the crankcases. The early style cylinder studs rely on an interfer-
ence fit between the threads of the case and the threads of the stud to prevent them
from coming loose. The late style studs have a looser thread fit, and are held in place
by a combination of thread tension and thread locking compound.
When the late style Evolution cylinder stud is tightened in the crankcase, the collar
bottoms on the crankcase base gasket surface and puts tension on the threads. This
tension pulls the threads of the crankcase and the stud tightly together. Without tight
metal to metal contact, the threads will be separated by a thin layer of thread locking
compound which is not capable of handling the compressive loads exerted on the cylin-
der stud by the head bolt.
S&S Evolution style crankcases currently being produced are equipped with late
style cylinder studs. Late style studs may be used to replace the early style, but they
must be installed with the collar down against the crankcase.
Occasionally, some older S&S Evolution Sidewinder big bore cylinders may contact
the collar on the late style cylinder stud. This prevents the cylinder from sliding all the
way down and contacting the crankcase deck. (See Figure 1) This is due to a combi-
nation of machining tolerances. The cylinder should slide over studs all the way down
to the base gasket surface of the crankcase without interference. Do not force the
cylinder down over the collar as distortion of the cylinder will result.
CAUTION - If cylinder is forced down over stud collar, cylinder will be distorted,
resulting in out of round cylinder bore. Stress created by forcing cylinder over
stud may also cause cracking of cylinder or cast-in iron cylinder liner. Cracks in
the cylinder or liner may result in engine failure.
WARNING - Engine failure due to cracked cylinder may result in personal injury
and/or loss of control of motorcycle.
Stud holes in current S&S cylinders have been drilled to a larger diameter to avoid
this problem. Older S&S cylinders can be modified using the procedure outlined below.
(See Figure 2)
1. Place cylinder on table of drill press or milling machine with base gasket surface up.
2. Select drill bit large enough to provide clearance for collar on cylinder stud (should
not require more than .500").
3. Set drill press stop so drill bit will not cut deeper than .100" below base gasket sur-
face of cylinder.
4. Center stud hole of cylinder under drill bit.
5. Clamp cylinder securely in position and carefully counterbore existing cylinder stud
hole to approximately .100" below base gasket surface. Use fairly low rpm and
slow feed rate to avoid catching the drill bit and potentially damaging the cylinder
and causing personal injury. Repeat for all stud holes.
6. Thoroughly clean all chips and foreign material from cylinder stud holes and oil pas-
sages with solvent and compressed air.
CAUTION - Metal filings, dirt and any other foreign contamination in the
engine oil may cause premature wear and/or irreversible damage to bearings
and other internal engine components.
WARNING - Compressed air and particles dislodged by compressed air are
harmful to eyes and body. Wear protective goggles when using compressed
air and always direct air stream away from body parts such as hands and
eyes. Never direct compressed air toward other people.
Service Bulletin #8
1-20-95
Copyright ©, 1994, 1995
by S&S Cycle, Inc.
All rights reserved.
Printed in the U.S.A.
S&S
®
Cycle, Inc.
Box 215
Viola, Wis. 54664
Phone 608-627-1497
Fax 608-627-1488
Figure 1 Figure 2
Cylinder
Cylinder
Crankcase Crankcase
Stud Collar
Stud Collar
Stud
Stud
Stud collar
prevents
cylinder from
contacting
crankcase.
Counterbore
cylinder stud
hole .100" deep