S&S Cycle, Inc Instruction .

S&S Cycle, Inc Instruction .
Instruction 51-1030
07-09-12
Copyright © 1986, 1995,
2006, & 2012
by S&S® Cycle, Inc.
S&S Cycle, Inc
®
.
14025 Cty Hwy G PO Box 215
Viola, Wisconsin 54664
Phone: 608-627-1497 • Fax: 608-627-1488
Technical Service Phone: 608-627-TECH (8324)
Technical Service Email: [email protected]
Website: www.sscycle.com
All rights reserved.
Printed in the U.S.A.
Installation Instructions: S&S® Sidewinder® 35⁄8" Big Bore Cylinders
for Harley-Davidson® Sportster® Models — 1986–2003
DISCLAIMER:
S&S parts are designed for high performance, closed course, racing
applications and are intended for the very experienced rider only. The
installation of S&S parts may void or adversely affect your factory warranty.
In addition, such installation and use may violate certain federal, state, and
local laws, rules and ordinances as well as other laws when used on motor
vehicles used on public highways, especially in states where pollution laws
may apply. Always check federal, state, and local laws before modifying
your motorcycle. It is the sole and exclusive responsibility of the user to
determine the suitability of the product for his or her use, and the user shall
assume all legal, personal injury risk and liability and all other obligations,
duties, and risks associated therewith.
The words Harley®, Harley-Davidson®, H-D®, Sportster®, Evolution®, and all
H-D part numbers and model designations are used in reference only. S&S
Cycle is not associated with Harley-Davidson, Inc.
SAFE INSTALLATION AND OPERATION RULES:
Before installing your new S&S part it is your responsibility to read and
follow the installation and maintenance procedures in these instructions
and follow the basic rules below for your personal safety.
•• Gasoline is extremely flammable and explosive under certain conditions
and toxic when breathed. Do not smoke. Perform installation in a well
ventilated area away from open flames or sparks.
•• If motorcycle has been running, wait until engine and exhaust pipes
have cooled down to avoid getting burned before performing any
installation steps.
•• Before performing any installation steps disconnect battery to
eliminate potential sparks and inadvertent engagement of starter
while working on electrical components.
•• Read instructions thoroughly and carefully so all procedures are
completely understood before performing any installation steps.
Contact S&S with any questions you may have if any steps are unclear or
any abnormalities occur during installation or operation of motorcycle
with a S&S part on it.
•• Consult an appropriate service manual for your motorcycle for correct
disassembly and reassembly procedures for any parts that need to be
removed to facilitate installation.
•• Use good judgment when performing installation and operating
motorcycle. Good judgment begins with a clear head. Don’t let
alcohol, drugs, or fatigue impair your judgment. Start installation
when you are fresh.
•• Be sure all federal, state, and local laws are obeyed with the installation.
•• For optimum performance and safety and to minimize potential
damage to carb or other components, use all mounting hardware that
is provided and follow all installation instructions.
•• Motorcycle exhaust fumes are toxic and poisonous and must not be
breathed. Run motorcycle in a well ventilated area where fumes can
dissipate.
IMPORTANT NOTICE:
Statements in this instruction sheet preceded by the following words are
of special significance.
WARNING
Means there is the possibility of injury to yourself or others.
CAUTION
Means there is the possibility of damage to the part or motorcycle.
NOTE
Other information of particular importance has been placed in italic type.
S&S recommends you take special notice of these items.
WARRANTY:
All S&S parts are guaranteed to the original purchaser to be free of
manufacturing defects in materials and workmanship for a period of twelve
(12) months from the date of purchase. Merchandise that fails to conform
to these conditions will be repaired or replaced at S&S’ option if the parts
are returned to us by the purchaser within the 12 month warranty period or
within 10 days thereafter.
In the event warranty service is required, the original purchaser must call or
write S&S immediately with the problem. Some problems can be rectified
by a telephone call and need no further course of action.
A part that is suspect of being defective must not be replaced by a Dealer
without prior authorization from S&S. If it is deemed necessary for S&S
to make an evaluation to determine whether the part was defective, a
return authorization number must be obtained from S&S. The parts must
be packaged properly so as to not cause further damage and be returned
prepaid to S&S with a copy of the original invoice of purchase and a detailed
letter outlining the nature of the problem, how the part was used and the
circumstances at the time of failure. If after an evaluation has been made by
S&S and the part was found to be defective, repair, replacement, or refund
will be granted.
ADDITIONAL WARRANTY PROVISIONS:
(1) S&S shall have no obligation in the event an S&S part is modified by any
other person or organization.
(2) S&S shall have no obligation if an S&S part becomes defective in whole
or in part as a result of improper installation, improper maintenance,
improper use, abnormal operation, or any other misuse or mistreatment
of the S&S part.
(3) S&S shall not be liable for any consequential or incidental damages
resulting from the failure of an S&S part, the breach of any warranties, the
failure to deliver, delay in delivery, delivery in non-conforming condition,
or for any other breach of contract or duty between S&S and a customer.
(4) S&S parts are designed exclusively for use in Harley-Davidson® and
other American v-twin motorcycles. S&S shall have no warranty or liability
obligation if an S&S part is used in any other application.
INTRODUCTION
Installation of an S&S® Harley-Davidson® Sportster® model 35⁄8" bore stroker Sidewinder® Kit is easy and can be performed by any Harley-Davidson®
repair shop equipped to do complete engine overhauls.
NOTES:
• To make installation of S&S Sidewinder series 35⁄8" bore kits easier, S&S has designed several Special Tools worth considering. They are:
Part 53-0002—Connecting Rod Checking Pin—helps check piston alignment in cylinder bore.
Part 53-0020—Degree Wheel Kit—used to check and set ignition timing and to check cam timing. This kit can also be used to check crankcase
breather gear timing in big twin engines.
Part 53-0006, 53-0007, and 53-0008—Crankcase Boring Fixture and Crankcase Boring Spacers—adapts most boring bars so crankcases can be
bored to fit larger diameter spigots on big bore cylinders. Enables qualified operator to bore cases in about an hour after initial setup. Can also be
used to bore pre-1984 style big twin heads when installing big bore cylinders.
• S&S pinion shafts for Evolution® Sportster® models are the 1987 style splined shaft because this design is stronger than the later style stock straight
shaft and key. As a result, the engine builder must use a 1986–1987 style pinion gear, S&S PN 33-4152 through 33-4156 (H-D® #24055-86 through
#24061-86) and oil pump drive gear, S&S PN 33-4228 (H-D® #26318-75). Stock Torrington® pinion main bearing in 1986 crankcases must be replaced
with 1987 race and later steel caged roller bearing. See Steps 6 and 10.
• Due to increased cylinder length, S&S Sidewinder kits of 96" and larger displacement require that stock cylinder studs be replaced with big twin
cylinder studs.
All reference to Harley-Davidson® part numbers is for identification purposes only. We in no way are implying that any of S&S® Cycle’s products are
original equipment parts or that they are equivalent to the corresponding Harley-Davidson® part number shown.
Read instructions thoroughly before starting work. When they are completely understood proceed with installation. It is strongly recommended
that the engine builder also obtain a copy of a Harley-Davidson® service manual of the same year as the engine being built.
INSTALLATION STEPS:
1. Clearance Frame*
2. Crankcase Alignment
3. Cylinder Mounting Studs (96” and larger engines only)
4. Bore Crankcases
5. Modify Crankcases for Oil Returning from Heads
6. Convert Pinion Main Bearing To 1987 and Later (1986 crankcases only)
7. Connecting Rod Preparation (79” engines only)
8. Lower End Assembly
9. Crankcase and Piston Skirt Clearancing
10. Connecting Rod Alignment*
11. Cylinder Head Preparation
12. Piston to Head and Piston to Valve Clearancing
13. Final Assembly and Engine Installation
14. Engine Break-In Procedure
15. Performance Notes
*NOTE: S &S recommends that engine builder consider performing some steps during initial engine removal and disassembly. Checking clearance
between stock engine and frame will allow an accurate estimate of amount and location of clearancing required after kit is installed. While
entire flywheel and rod assembly may be replaced, it is sometimes helpful to check original parts combination and note problems that can be
corrected more easily before engine is reassembled.
2
INSTALLATION
1. Clearance Frame
NOTE: P
iston stability in cylinder bore is improved by using pistons with the longest possible skirts. In order to provide a performance engine with the best
possible engine life, S&S increases the cylinder length when the stroke is increased, rather than decreasing the length of the piston. Frame fit, stock
rocker cover to frame tubes and/or rocker cover to gas tank clearances in taller than stock engines must be checked and corrected if needed. It is
recommended that frame clearance be measured before stock engine is removed from frame. The 89" Sidewinder kit is the largest engine that will
fit in a stock frame without major frame modifications.
To check and clearance frame, perform following steps:
A.Before stock engine is removed from frame, measure clearance between rocker boxes and frame. Tightest spot is normally above and
behind rear head.
Kit Part
Number
Displacement
Stroke
Cylinder Length
Cylinder Length
Compared to Stock
91-3002
79"
313⁄16"
4.650"
Stock Length
91-3121
91-3123
89"
415⁄16"
5.087"
+.437"
106-5834
CTO
Chart 1
B.Refer to chart 1, above, to determine increase over stock engine height for the kit to be installed. S&S® recommends .100" minimum
clearance between engine and frame. If increased cylinder height of Sidewinder® kit will not leave sufficient room, clearancing will be
required. S&S cylinder heads for Harley-Davidson® Sportster® models are .062" taller than stock, so additional clearance will be required if
S&S heads are to be used.
NOTE: S &S recommends there be .100" minimum clearance between engine and frame. Up to .060" or .070" may be ground from rocker box cover in some
areas for clearance. If cover is ground, be careful not to break through since covers are very thin.
CAUTION
Excessive material removed from rocker cover may damage cover causing oil leaks.
WARNING
Removing material from welds or frame tube may cause structural damage and possible failure resulting in personal injury or death. If
frame must be modified, work should be done by a professional frame shop.
C.After crankcases have been bored in Step 4, mock up engine using Sidewinder cylinders. Place mocked up engine in frame and determine
if additional clearancing will be needed to provide recommended .100” space between engine and frame.
2. Crankcase Alignment
NOTE: S ome crankcase base gasket surfaces on which cylinders are positioned do not align properly. This usually occurs when crankcase halves used
are from different crankcase assemblies and were not paired and machined together during manufacture. It is recommended that crankcases be
checked for misalignment even if crankcase halves are correctly matched to prevent potential oil leaks and other mechanical problems.
CAUTION
Mismatched gasket surfaces due to improperly aligned crankcase halves may cause oil leaks.
A. Clean cases thoroughly and assemble both halves without flywheels. Tighten all case bolts as in final assembly.
B. Place straight edge ruler across base gasket surface. See Picture 1, next page.
C. If crankcase halves are correctly aligned, proceed to Step 3. If any misalignment exists got to Step D in this section.
D.Remove cylinder studs and place masking tape over cam and mainshaft bearings to keep chips out. Consult Harley-Davidson® service
manual for proper cylinder stud removal and installation procedures.
CAUTION
Be careful when removing studs so as not to damage threads in cases. If heat is applied to case around stud to help loosen threads, do
not allow crankcase temperature to exceed 375° F as this may destroy heat treatment of crankcase material.
3
Picture 1
E.Place cases squarely in mill. Base gasket surface must be square with center line of crankshaft and 45° from opposite cylinder base gasket
surface. Machine gasket surface taking minimum necessary to clean surface. Repeat for other cylinder.
F.Reinstall cylinder studs. For engines under 96" (45⁄8" stroke) reinstall original studs. For engines of 96" or larger install late big twin style
studs. (See Step 3) Consult Harley-Davidson® service manual for proper stud installation procedure.
3. Cylinder Mounting Studs—96" Engines and Larger only
NOTE: S &S Sidewinder kits for Evolution® Sportster® models of 96" (45⁄8" stroke) or greater require the use of big twin cylinder studs. This is due to the
increased cylinder length in these kits.
A.Remove stock cylinder studs if this has not been done in Step 2. Consult Harley-Davidson® service manual for proper stud removal
procedures.
CAUTION
Be careful when removing studs so as not to damage threads in cases. If stud does not come out easily, carefully heat case around stud
as heat may help loosen threads. Do not allow crankcase temperature to exceed 375° F, as this may destroy heat treatment of crankcase
material.
B.Install late big twin male type studs, S&S 31-2321, or Harley-Davidson® part #16837-85C. Consult Harley-Davidson® service manual for
proper installation procedures.
4. Bore Crankcases
NOTE: Boring cylinder spigot holes in cases to accommodate big bore cylinders will machine a notch on center case bolt. This bolt must be replaced with
a special stud which is installed into the top crankcase bolt hole in the cam side case half.
Perform following procedure to bore crankcases:
A.In 1986–1990, four speed cases, the center crankcase bolt must be replaced by S&S® stud 31-2046. In 1991 and later, 5 speed cases, the
center crankcase bolt must be replaced by S&S stud 31-2047. The stud will be installed in the threaded hole in the camside crankcase
half that the stock center crankcase bolt normally screws into.
1.Before final installation of stud, screw stud into hole to make sure installed height is correct. See Picture 2, below left. Stud should
extend 2.570"–2.630" from crankcase to top of stud for 1986–1990 crankcases, and 2.270"–2.330" from crankcase to top of stud for
1991 and later crankcases. If driveside case is set in place, stud should extend far enough that there is full thread engagement with 12
point nut 50-5024 when washer is in place. See Picture 3, below right.
Picture 2
Picture 3
4
2.If stud can not be screwed in far enough to obtain specified stud height, hole must be drilled and tapped deeper. It is recommended
that this drilling operation be done on a milling machine or drill press to avoid destroying existing threads.
3.If stud can be installed to correct height, clean stud and threaded hole with lacquer thinner and install stud to correct height using
red Loctite® or other permanent thread locking compound.
B. Clean cases thoroughly and assemble using all case bolts. Tighten all case bolts as in final assembly.
C.Place masking tape over both ends of camshaft and mainshaft bearings to keep chips out.
D.Bolt boring plate to bench or stand leaving squared end of plate protrude over edge approximately 7".
E.Using 43⁄8 -16 thread nuts, bolt cases to plate using all four studs. Boring spacer, Part 53-0007, is used to space cases using stock HarleyDavidson® Sportster® models studs. If Sportster® model studs have been replaced with late, male style big twin studs, use both 53-0007
and53-0008 spacers to space cases away from boring fixture. See Picture 4, below.
NOTE: Be careful not to damage studs. Do not lift cases by studs and avoid knicking, scratching or denting studs.
Picture 4
CAUTION
Damaged studs may cause stress risers which can lead to stud failure and possible damage to engine components.
F.Center boring bar head in cylinder spigot bore in crankcases, not hole in plate. Refer to manufacturer’s instructions supplied with
boring bar for correct procedure.
G.Bore hole to diameter of 3.878" to 3.880" by 15⁄8" deep. Measure depth perpendicular from cylinder base gasket surface.
NOTE: W
e normally take three cuts to bore cases, 3.800" diameter, 3.850" and final size 3.879". If you machine into boring plate on final cut, this is of no
consequence since hole in plate is never used as machining reference point.
H.Repeat steps E to G for other spigot bore.
I.Deburr and remove any nubs or protrusions which could accidentally break off. Break the corner on outside of spigot holes with a
deburring tool. This insures that cylinder will not hang up during installation causing oil leaks due to inadequate gasket compression.
Figure 1, next page top left, shows an exaggerated view.
5
Grind four (4) oil groves
on both sides of forked rod
Figure 2
Figure 1
5. Modify Crankcases for Oil Returning from Heads
NOTE: O
il return passageways in Sidewinder® cylinders are moved out slightly compared with stock oil return holes to accommodate 35⁄8" bore. This
creates misalignment between cylinder oil return passage and crankcase oil return passage.
To modify cases and return oil properly, perform following steps:
A.Place cylinder base gasket on cases and note amount and direction of return hole mismatch.
B. Chamfer edge of hole accordingly at minimum of 45° angle to insure adequate flow. See Pictures 5, below left, and 6, below right..
Picture 5
Picture 6
6. Convert Pinion Main Bearing
To 1987 & Later Style (1986 crankcases only)
A.Remove stock Torrington® style pinion needle bearing assembly. Follow procedures outlined in 1986 Harley-Davidson® service manual for
removal.
B. Install 1987 and later style pinion bearing race H-D® #8881. Follow procedures outlined in 1987 and later Harley-Davidson® service manual.
C. Lap bearing race and fit bearings per procedures outlined in 1987 and later Harley-Davidson® service manual.
All reference to Harley-Davidson® part numbers is for identification purposes only. We in no way are implying that any of S&S® Cycle’s products are
original equipment parts or that they are equivalent to the corresponding Harley-Davidson® part number shown.
7. Connecting Rod Preparation (79" kits only)
NOTE: If S&S® connecting rods are used, follow instructions that accompany rods since rod preparation below has already been done. Stock rods can not
be used with Sidewinder kits larger than 79". Longer than stock S&S connecting rods will be provided with all kits larger than 79".
79" kit 91-3002 only—If S&S rods are not used, perform following steps:
A.To insure adequate oil on sides of rods and matching thrust surfaces of flywheels, S&S recommends that four grooves be ground on each
side of both front and rear connecting rods. See Figure 2, above right. Make these grooves .020" to .030" deep and .030" to .040" wide
and should be ground 90° from each other. After making grooves, remove all sharp edges and burrs with emery cloth.
B. Thoroughly clean all parts to remove dirt, filings, etc.
CAUTION
Burrs, dirt, filings, etc. left on connecting rod components may circulate in oil damaging other parts possibly causing engine failure.
6
8. Lower End Assembly (All)
NOTES:
• All current production S&S® Evolution® Sportster® model flywheels are made from closed die, heat treated, steel forgings. They do not have
connecting rod thrust washers like earlier S&S or stock flywheels, because present flywheel material is harder than thrust washers previously used.
• S&S Sportster® model style flywheels come with three timing marks, “F”, “R” and “TF”. The “F” mark stands for front cylinder 30° before top dead
center (TDC). The “R” mark is rear cylinder 30° before TDC, The “TF” mark is TDC front cylinder. When “F” or “R” mark is placed in center of timing
hole it means that cylinder is timed at 30° before TDC. We recommend that big inch Sportster® engines be timed at 30–32° before TDC rather than
the stock 40° before TDC. See Performance Notes, Ignition Timing.
• Usually S&S flywheels are balanced before leaving our facility. Some customers prefer to do their own balancing or to have another balancing shop
do the work for them. This is acceptable in most cases. However, we have had some bad experiences with dynamically balanced flywheels that have
forced us to void our guarantee if flywheels have been balanced in this fashion.
CAUTION
Flywheels assembled improperly prior to being dynamically balanced may sustain irreversible damage to mainshaft and crankpin
tapers during actual balancing. S&S voids its guarantee if flywheels have been balanced in this fashion.
• Many problems in assembling and truing flywheels can be prevented by careful inspection of all parts used in the assembly.
• Cleaning parts prior to and during assembly and keeping parts clean after final assembly are imperative to minimize contaminants that may
circulate in oil and shorten engine life. Many parts can be cleaned with soap and water first. Then, reclean all internal parts and gasket mating
surfaces using high quality solvent that does not leave any harmful residues. Be sure to read and follow manufacturer’s instruction label before use.
Use drills and compressed air to clean all oil passageways of dirt, filings, etc. whenever possible. During actual final assembly, recoat all internal
parts with high quality engine oil or assembly lube such as S&S 51-9000.
CAUTION
Manufacturing chips, dirt and/or other contaminants circulating in engine oil may possibly damage engine components resulting in
shorter engine life and possible engine failure.
WARNING
• Some solvents, degreasers, gasoline and other chemicals are harmful to skin, eyes and other body parts. Many items are flammable
and present a fire hazard. Read manufacturer’s instruction label for proper use. Use in well ventilated area and wear protective
clothing when using them to avoid personal injury.
• 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.
Perform following steps when assembling flywheels:
A.Thoroughly clean all parts to be used. This includes mainshafts, main bearings, connecting rods, rod bearings, keys and flywheels
including tapers and key ways.
CAUTION
Burrs, dirt, filings, etc. left on flywheel assembly parts may circulate in oil damaging other parts possibly causing engine failure.
B. Inspect key ways and oil holes in flywheels for burrs and remove if necessary.
NOTE: S&S does not recommend lapping tapers to remove burrs. This practice tends to distort the taper by removing material unevenly around the
circumference. This makes flywheels difficult if not impossible to true. In addition the lapping process work hardens the surface of the taper. This
hard surface makes it very difficult to pull shaft or crankpin into taper. If crankpin and shafts are not pulled fully into flywheel tapers, excessive rod
side play and assembly width may result. Lapped flywheel tapers are also very difficult to resurface if repairs are ever needed.
CAUTION
S&S warranty is void if flywheel tapers are lapped.
C.Check keys in grooves of shafts. Key should be light hand press fit in groove. If key is too tight in groove, sand side key with fine sand
paper on a metal plate or other flat surface. Do not hammer key into groove.
CAUTION
Hammering tight key into groove may result in irreparable damage to shaft.
7
D.With key in shaft, insert into respective tapered hole in flywheel and check to see that key does not bottom in groove. If key bottoms
out, file flat side of key, not rounded side, until shaft with key in place fits in flywheel without bottoming out. Check crankpin and
crankpin key also.
E. Reclean mainshaft tapers, crankpin and flywheel tapers with lacquer thinner.
F.Assemble mainshafts in respective flywheels. Coat taper and threads of each shaft with green Loctite® during assembly. Install crankpin
in camside flywheel using Loctite® also. Tighten crankpin nuts to 290–310 ft. lbs. Tighten pinion and sprocket shaft nuts to 340–360 ft.
lbs.
G.After camside flywheel, pinion shaft, and crankpin are assembled, blow air through pinion shaft oil feed hole to check for blockage or
misalignment of oil feed passages.
CAUTION
Partially or completely blocked oil feed passageways may cause irreversible damage to connecting rod bearings and other engine
components.
H.Measure width of female rod on crankpin end. See Picture 7, below. Measurement should be 1.481" to 1.483".
Picture 7
I.A pre-assembly connecting rod side play check should be done before final assembly to determine if connecting rod side play will fall
within the specified .015"–.035" range when crankpin nuts are final tightened. Assemble left and right flywheels on crankpin without
rods. Moderately snug crankpin nuts. Do not worry about flywheels being true. Measure distance between connecting rod thrust
pads on flywheels. See Picture 8, below. Rod side play will be reduced by about .015" when crankpin nut is final tightened. Therefore,
distance between flywheel thrust pads as measured in this check must be .030"–.050" greater than female rod width measured in Step
H. For example, if female rod measures 1.482", the distance between flywheel pads must be 1.512"–1.532". If difference between pad to
pad distance and female rod width is less than .030", female rod must be surface ground on sides to provide more clearance. Take equal
amounts off each side if more than .010" is to be removed. If more than .050” must be removed from female rod width or if difference
between pad to pad distance and female rod width is greater than .050" a different crankpin should be tried. If there is too little or too
much connecting rod side play, and different crankpins do not correct problem, contact S&S®.
NOTE: S &S recommended rod side play is .015" to .035". If material is removed from sides of female rod, overall width of bearing cages must be reduced
so bearings and cages are free to float with rods without contacting flywheel thrust pads. Bearing cage side clearance of .008" to .020" less than
rod width is recommended.
Picture 8
8
CAUTION
• Incorrect connecting rod side play may cause excessive rod side thrusting and potential damage to rods, flywheels and other engine
components.
• Connecting rod bearing and cage assemblies that are wider than female rod may become damaged upon contact with flywheel thrust
pads. Abrasive particles from damaged rod bearings may circulate in oil and cause damage to other engine parts.
J. Finish assembling flywheels and rods.
K.Check flywheel assembly for run out by placing ends of mainshafts between centers. Place dial indicators on bearing surfaces of
mainshafts. See Picture 9, below. True wheels as needed. S&S trues flywheel assemblies to .0005" or less runout on either mainshaft
bearing surface. However Harley-Davidson® factory specs call for .001" runout and this is acceptable.
Picture 9
NOTES:
• When truing flywheels, runout measurements must be taken on mainshaft bearing surfaces. Do not take measurements on flywheel rims. Flywheel
rim will show runout that is not a valid indication of mainshaft concentricity.
• Do not install flywheels and final assemble crankcases until clearances are checked in Step 9.
9. Crankcase and Piston Skirt Clearancing (All)
NOTE: M
any of the clearancing operations described in this section can be done simultaneously as the same set-ups are used. Please read this entire
section before beginning work.
CAUTION
Insufficient clearance between connecting rods and crankcases, pistons and flywheels, and between the two pistons will cause contact
and damage to components.
A.Connecting Rod Clearance - Front and rear of flywheel cavity inside crankcases and cylinder spigots must be clearanced for connecting
rods. See Pictures 10, below left, and 11, below right. Procedure to check these points is performed as follows:
1.Mock up flywheel assembly in right crankcase half with bearings, etc. in place.
2.Assemble pistons without rings on their proper connecting rods, and place connecting rods on crankpin. Installation of wristpin clips
is not necessary.
Picture 10
Picture 11
9
NOTE: A
ll S&S® Sidewinder® kits have piston to piston clearance notch cut in the front skirt of rear piston. Rear piston must be installed with notch toward
the center of engine.
3.Install both cylinders and secure each with one head bolt.
4.Rotate flywheel until rods contact areas to be clearanced. Note angle that must be filed.
5.Disassemble cylinder and connecting rods and file crankcase and cylinder spigot for clearance. See Picture 12, below.
NOTE: A minimum of .060" clearance is required between connecting rods and crankcase and cylinder spigots.
Picture 12
6.Reassemble and check clearance.
7.Mark and grind other crankcase half to identical clearance.
B.Piston Clearance - Piston clearances must be checked to avoid piston to piston contact and piston to flywheel contact. See Pictures 13,
below left, and 14, below right.
Picture 13
Picture 14
NOTE: Pistons are normally clearanced in S&S kits, but good engine building practice demands that all clearances be checked during assembly. In the
event that additional clearancing must be done, weight of material removed from pistons generally is too small to significantly affect flywheel
balance.
1. Piston to Piston Clearance
a.Perform Steps 1 through 3 in Connecting Rod Clearance (Step A, page 9).
b.Rotate flywheel to position where pistons are closest to each other. This is at the bottom of the stroke. See Picture 13, above left.
c.Check clearance between pistons.
NOTE: A minimum of .060" clearance is required between piston skirts at the bottom of the stroke.
d.If clearance is not sufficient, disassemble cylinders and pistons, and carefully file notch in front skirt of rear piston until clearance is
obtained.
NOTE: T he rear skirt of the piston is the primary thrust face, and carries the greatest load during engine operation. For this reason, piston to piston
clearancing is done on the front skirt of the rear piston in order to leave the rear skirts of both pistons as long as possible.
e.Reassemble and recheck clearance.
10
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.
Figure 3
CAUTION
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: P
inion 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.
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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, below left.
2.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.
3. Repeat checking and bending procedure for the other rod.
Picture 15
Figure 4
C. Visual Procedure
1. Install pistons on rods without rings or wristpin clips. Bolt cylinders with gaskets in place.
2. Move piston tight towards camside of engine.
3. Turn engine over in normal direction of travel 2 or 3 revolutions and observe piston during process.
4.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 4 , above right, shows an exaggerated side view
of this condition.
5. Repeat Steps B to D for other cylinder.
11. Cylinder Head Preparation
A. Head Gasket Surface Flatness Check - Before top end is assembled, head gasket to cylinder mating surfaces should be checked as follows
1. Thoroughly clean cylinder head gasket surfaces.
2. Place straight edge ruler across head gasket surface at different places around diameter to determine flatness.
3. If unevenness is revealed, machine head gasket surface just enough to make complete contact.
CAUTION
Incomplete contact between gasket surfaces of cylinders and cylinder heads may cause combustion leakage possibly resulting in
damage to cylinders and/or other engine components.
B.Modify 883 Cylinder Head Combustion Chamber - If 883cc cylinder heads are to be used, the combustion chambers must be modified to
improve air flow and reduce the compression ratio. Follow enclosed Instruction Sheet #3883 or #3884 depending on style of combustion
chambers in heads to be used. 1200cc heads do not require this modification.
NOTE: Stock 1200cc heads or modified 883 heads will provide a usable compression ratio but the small valves and ports in stock heads will be a limiting
factor for a large displacement performance motor. To achieve the full potential of the engine it is recommended that the size of the valves be
increased and the ports modified to further improve flow. In weighing the expense and difficulty of these modifications, it may be more cost
effective and results intensive to use S&S® or other aftermarket performance heads.
12
12.Piston to Head & Piston to Valve Clearancing
NOTES:
• The clearancing operations described in this section can be done simultaneously as the same set-ups are used. Please read this entire section before
beginning work.
• All valve spring spacing, rocker arm to collar and rocker arm to rocker cover clearancing must be done before piston to valve clearancing can be
checked.
• S&S® flat topped pistons have sufficient valve clearance when used with most street high performance cams with lifts up to .525". However, we
recommend that valve clearancing be checked if other than stock cam is used.
• If S&S cylinder heads and pistons are used, cams of up to .560" lift can be run without valve to piston clearance problems. If cams with higher lift are
used this clearance must be checked.
CAUTION
Improper installation of pistons may cause unwarranted stress, premature wear and/or contact with each other or other engine
components resulting in damage to pistons or other engine parts.
• If there is any resistance or contact at any point in rotation it must be diagnosed and corrected. Since it is nearly impossible to anticipate every
possible engine combination, it is the engine builder’s responsibility to check for proper running clearances. S&S considers checking and establishing
all running clearances as standard engine building practice that must be performed during engine assembly. Engine failure due to improper
clearances between moving parts is not covered under warranty.
CAUTION
Contact between moving engine components may cause damage or destruction of the parts involved and produce abrasive particles
which may cause damage or premature wear to other engine components.
A. Piston to head (squish) clearance
1. Assemble engine with exception of cylinder heads.
NOTE: P
inion Shafts included with S&S flywheels kits and assemblies for Evolution® Sportster® models 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.
2. Rotate flywheels so front piston is positioned at top dead center.
Figure 5
3.Note where piston deck (See Figure 5, piston deck diagram) is positioned in relationship to head gasket surface. Piston deck (flat
located just above top compression ring groove), not dome, must be flush with or slightly below gasket surface.
4.If piston deck is higher than cylinder at top dead center, something is wrong and S&S should be notified. If piston deck position is
correct proceed to Step B.
NOTE: M
ost stock V-Twin and S&S engines are designed with .045" to .062" piston to head clearance. This clearance is provided by thickness of head
gasket. Therefore at top dead center, piston deck should be flush with or slightly below head gasket surface of cylinder. Cylinder base gasket must
be in place when this check is made.
CAUTION
Insufficient clearance between piston domes and cylinder heads will cause damage to pistons and heads.
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B. Piston to Valve Clearance
1. Turn engine over until piston in front cylinder is at top dead center. Paint area around valve pockets on pistons with machinist’s blue.
2. Place valves in cylinder head leaving off springs and retainers. Place head on cylinder and secure with one bolt.
3. Lower valves until they contact piston. Rotate valve marking painted area.
4. Remove head and check points of contact. Valve should fit in recessed area machined in piston dome.
NOTE: S&S recommends at least .060" clearance around periphery of valve.
5.If insufficient clearance exists, remove piston and grind valve pocket until head of valve fits flush with proper clearance. Clean parts
thoroughly before reassembly.
CAUTION
Do not remove more material than needed when performing piston to valve clearancing. Removal of excessive amounts of material
may weaken top ring land of piston causing piston breakage and serious engine damage.
6. Repeat procedure for other cylinder head.
7. Spread layer of putty into valve pockets in both pistons.
8. Assemble cylinder heads and bolt assemblies on cylinders with head gaskets in place. Install pushrods and adjust to simulate final
assembly.
NOTE: I f hydraulic lifters are used, pushrods should be adjusted so that lifters are completely collapsed for this test. This will insure that lifters do not
collapse due to valve spring pressure, and that full valve lift is achieved.
9. Turn engine over in normal direction of travel two complete revolutions.
10. Remove cylinder heads and check thickness of putty in valve pockets.
11.If clearance is sufficient, disassemble top end and proceed to final assembly.
12.If less than .060" clearance in any area exists, remove piston from engine and grind area until proper clearance is achieved. Clean
parts thoroughly before reassembly.
NOTE: S &S® recommends at least .060" clearance between valve and piston valve pocket recess. While .060" clearance is recommended minimum, it is
advisable to have more, if possible.
CAUTION
Insufficient clearance between piston and valves may cause them to contact each other during operation resulting in damage to piston
and valve train components.
13.Final Assembly and Engine Installation
NOTE: C
leaning parts prior to and during assembly and keeping parts clean after final assembly are imperative to minimize contaminants that may
circulate in oil and shorten engine life. Many parts can be cleaned with soap and water first. Then, reclean all internal parts and gasket mating
surfaces using high quality solvent that does not leave any harmful residues. Be sure to read and follow manufacturer’s instruction label before
use. Use drills and compressed air to clean all oil passageways of dirt, filings, etc. whenever possible. During actual final assembly, recoat all
internal parts with high quality engine oil or assembly lube such as S&S 51-9000.
CAUTION
Manufacturing chips, dirt and/or other contaminants circulating in engine oil may possibly damage engine components resulting in
shorter engine life and possible engine failure.
WARNING
• Some solvents, degreasers and other chemicals are harmful to skin, eyes and other body parts. Many items are flammable and
present a fire hazard. Read manufacturer’s instruction label for proper use. Use in well ventilated area and wear protective clothing
when using them to avoid personal injury.
• 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.
A Spin each head bolt down on its respective stud to be sure threads are clean and free of contamination.
B. Install cylinder base gaskets provided dry. Be sure gaskets match cylinder base line-up dowels and oil return passageways.
14
C. Install pistons, rings and wristpin clips per S&S piston instruction sheet 51-1028.
D. Coat piston skirts with engine oil or assembly lube and install cylinders.
E. Place o-ring seals over cylinder head alignment dowels. Install head gaskets provided in kit dry.
NOTE: C
are must be taken to use correct alignment dowel o-rings with 1986 and later Sportster® models head gaskets. Head gaskets supplied with S&S
cylinder heads compress to about .045” thick and require .070" diameter o-rings. Gaskets supplied with Sidewinder® for stock heads compress to
about .0625" and require .0825" diameter o-rings.
CAUTION
Using thin o-rings with thick gaskets or thick o-rings with thin gaskets may cause oil leaks or possible ruptured head gaskets around
line-up dowels due to incorrect o-ring compression.
NOTE: All S&S cylinder head kits are supplied with .045” thick head gaskets, because this clearance promotes better combustion chamber turbulence
and flame travel. When other cylinder heads are used S&S supplies .0625" thick gaskets. Using thicker head gaskets with S&S heads reduces design
efficiency and performance. If thinner head gaskets are used with other cylinder heads, piston to head and valve to piston clearances must be
checked during assembly.
CAUTION
Insufficient clearance between piston domes and cylinder heads or piston domes and valves will cause damage to pistons, heads and/
or valves.
F.Bolt heads on cylinders. Place one or two drops of oil on threads of each head bolt just prior to final assembly to reduce friction and
insure accurate torque readings. Tighten bolts in stages using crossing pattern. See Figure 6. If using S&S crankcases, torque bolts to
45-47 ft. lbs. in four stages. If using stock crankcases, follow the same bolt tightening sequence, but use stock three stage procedure and
torque values shown in Figure 6. If using other aftermarket crankcases, contact the manufacturer for recommended head bolt torque
specifications.
Top View
Driveside
1
2
2
1
3
4
4
3
Camside
S&S® Crankcase
Stage 1
7–9 Ft. Lbs.
Stage 2
12–14 Ft. Lbs.
Stage 3
Turn additional 90°
Figure 6
NOTE: L ight coating of oil on head bolt threads minimizes friction so torque values are not distorted. It cannot be emphasized enough how important it
is to do these steps carefully. Maintaining a good head gasket seal depends on it.
CAUTION
Improper torquing sequence and head bolt torque values may cause head gasket failure. Excessive torque values may cause studs to
pull out of crankcase.
G. Finish Assembling Top End
1. Install rocker arm bases per Harley-Davidson® specs.
2.1991 and later five speed models only—Stock one piece pushrod tube assemblies on 1991 and later five speed engines must be
replaced with 1986 to 1990 style two piece pushrod tubes to allow adjustment of pushrods. Installation of 33-5360 S&S® pushrod tube
adapter provides cup for bottom of earlier style pushrod tubes. Place stock pushrod retainer over small end of adapter. Slide stock
pushrod seal on small end of adapter. Install adapter, retainer, and seal over tappet bore in crankcase with stock bolt and washer. Do
not final tighten. See Picture 16, next page.
15
Picture 16
3.Assemble rocker arms, pushrods and pushrod tube assemblies and adjust pushrods. For 1991 and later five speed motors, place bottom
end of 1986 to 1990 pushrod tubes in cup of adapter. Use stock 1986 to 1990 pushrod seals. Rotate S&S pushrod tube adapters so that
cup surface is as close to perpendicular with pushrod tube as possible. Install pushrod cover clip and final tighten stock pushrod tube
retainer bolt.
4. Install rocker covers and gaskets.
5.Install intake manifold, mounting flanges and o-ring seals. Be sure o-rings and flanges are assembled in correct sequence. Tapered side
of o-ring must fit into tapered side of flange. See Figure 7. Use flange marked “F” on front head and flange marked “R” on rear. Slotted
end of mounting flange goes toward lower manifold mounting hole. Flat washer provided is used on slotted end of flange. Do not
tighten mounting flange screws.
NOTE: If S&S heads are installed, special S&S manifold must be used because intake port diameters of S&S heads are larger than stock. Special S&S
manifold requires o-ring seals which also have larger than stock diameter to fit O.D. of manifold runners. These o-rings, S&S part 16-0235, are
included and cannot be used in stock applications.
Figure 7
CAUTION
Incorrect o-ring seal may cause air leaks around manifold resulting in lean condition and possible damage to engine.
H.Bolt carburetor and air cleaner assembly in place using carburetor instructions supplied from manufacturer. Final tighten manifold
mounting flanges.
NOTE: Some builders may prefer to install carburetor after engine is installed in frame to reduce the possibility of damage to carb.
I. Install engine in frame according to Harley-Davidson® factory procedures.
NOTE: The stock head mounts, when used with longer than stock cylinder lengths will be short. Use the special S&S head mounts provided.
J.Reassemble gas tanks and all other parts that were dissembled during preparation for top end service. Be sure there are no gasoline leaks
and that throttle opens and closes smoothly and snaps shut when released.
NOTES:
• Throttle must not bind and must snap shut to fully closed position when released.
• Fuel needle and seat assembly must completely shut off fuel supply entering bowl. Fuel line connections must not leak.
16
CAUTION
Unwarranted gasoline leaking by fuel inlet needle may flood engine causing damage to components.
WARNING
• If throttle does not return to fully closed position when released, it may inadvertently stick open possibly causing loss of control of
motorcycle and personal injury to you or others.
• Unwarranted gasoline leaks at fuel line connections and/or past inlet needle may flood engine and overflow on surrounding area
creating fire hazard.
14.Engine Break-In Procedure
A.Upon initial start-up, quickly check to make sure oil pressure is normal and no leaks exist. With minimal load on engine, ride motorcycle
at low speeds until cylinder head temperature reaches about 250°. Do not crack throttle or subject engine to any heavy load during this
period as head gaskets are susceptible to failure until heat build-up is completed. Heat build-up is necessary to cause heads and cylinders
to expand and seal. Improper initial engine start-up and break-in procedure may cause head gasket failure.
CAUTION
Do not allow engine temperature to become excessive as permanent engine damage may result.
B.First 50 miles are most critical for new rings and piston break-in. Most engine damage will initially occur during this period. Keep heat
down by not exceeding 2500 RPM. Vary speed. Do not lug engine.
C.Next 500 miles should be spent running engine no faster than 3500 RPM or about 50-55 mph. Do not lug engine and continue to vary
speed.
CAUTION
Lugging or running engine prematurely at high RPMs may result in damage to pistons and/or other engine components. S&S® voids its
guarantee if engine is not broken in properly.
D.For balance of first 1000 miles, speed can be run up to 60 to 70. Continue to run engine at all different speeds including lower 40–45 mph
ranges.
E.1000 to 2000 miles—basically same procedures as before. You can be a little more liberal with RPM range. Avoid overheating engine and
putting any hard strain on engine (drag racing, trailer towing, sidecar operation).
G. 2000 miles and up—have fun!
15. Performance Notes
Ignition
• Ignition system type—Most S&S engines initially tested on our dyno are equipped with an aftermarket high performance electronic unit. These
systems allow us to bypass the performance parameters (such as the RPM limiter) designed for stock parts and built in to the stock ignition system.
• Spark plugs—Use spark plugs that are compatible with the ignition system. If you are in doubt, most manufacturers can recommend which plugs
they prefer you use with their system. Dual plug installations in S&S Super Stock® heads are not necessary.
• Flywheels—S&S flywheels for Evolution® Sportster® models have timing marks for front and rear cylinders. Both flywheels have timing marks to
accommodate both four speed and five speed engines. The “F” mark is front cylinder 30° advanced (before TDC). The “R” mark is rear cylinder 30°
advanced. When “F” or “R” timing marks are located in the center of the timing hole, the crankshaft is positioned 30° before TDC for that cylinder.
Placing the mark to the rear of the hole, or just entering the hole, advances timing almost 5°. Conversely, if the mark is just leaving the hole, timing
is retarded almost 5°.
• Timing—Tests conducted using S&S Super Stock® heads and modified stock Harley-Davidson® heads showed that best performance was
achieved with the ignition timing set between 30–32° before TDC. We attribute this to the higher compression ratios generally used, improved
flow characteristics and improved overall efficiency. If using stock heads, the higher the compression ratio less advance is generally needed.
Lower compression engines may require more advance. Some experimentation may be required to determine the best timing setting for best
performance. Once the engine is timed and operating, monitor it for excessive heat. Too much heat can mean that timing is set incorrectly and
should be adjusted to prevent engine damage.
CAUTION
Improper ignition timing may cause excessive engine heat which may damage pistons and/or other engine components.
17
Carburetion
• All S&S® test engines are run using S&S carburetors. S&S Super E and G carburetors are recommended for most applications with the Super G
being used more often on larger displacement, freer breathing engines with higher compression ratios. Typically, engines equipped with S&S heads
require the same or slightly leaner jetting than those engines fitted with stock heads. Consult the carburetor jetting instructions for specific jetting
recommendations.
• If another type carburetor is used, it must be made to run rich enough to operate properly and to prevent engine damage. If you have a problem
with another carburetor, S&S cannot help you and recommends you call the carb manufacturer with any questions you may have.
• If the motorcycle is used exclusively on a drag strip where engine temperatures vary, slightly richer jets may be necessary for best performance.
Larger jets/richer mixtures will enable one to run a colder engine which is sometimes desirable. This is best determined by experimentation.
• Carburetor jetting and spark plug color—While spark plug color may be used to help determine carburetor jetting, S&S recommends that our
instructions be used as primary jetting guide and that plug color indications be used only as secondary aid. We have found that different brands
of gasoline, gasoline additives, engine heat (due to ignition timing), and brands of plugs and heat range used distort plug color drastically making
plug reading difficult for the average tuner. Also, new plugs usually require a road test of 10 miles or more to properly develop the color which
means that quarter mile tests may not be long enough and hence, not always a good indication of carb jetting. It is best to use proven spark
plug combinations and to consult the spark plug manufacturer if you have questions. If one desires to become more proficient at plug reading,
Champion Racing Division has a very informative booklet which may be helpful. For details, write:
Champion Spark Plug Co.
PO Box 910
Toledo, OH 43601
• Cams and exhaust systems can make some engines difficult to carburate. We have found that certain cams and exhaust systems will cause poor
performance at a specific RPM, and attempts to correct jetting for that specific level usually destroys carburetion over the balance of the range. A
combination of cam overlap, reversion, and back pressure, or even lack of back pressure can cause mixture dilution at certain engine RPMs. This
dilution will cause engine roughness or misfiring when engine is held in this range.
Exhaust Systems
• Drag pipes—While drag pipes can be used with good results to establish performance guidelines on pre-1984 engines, they are generally not
recommended for 1984 and up big twin engines in street applications. Big twin engines are easier to carburate with muffled systems.
• Muffler systems—Most stock and many aftermarket exhaust systems are too restrictive and made exclusively for looks with little consideration
given to performance. A very good, economical street system consists of the stock header pipes with the crossover tube and a set of low restriction
mufflers. S&S offers a line of slip-on mufflers that create performance economically. This combination will typically produce 10 hp more than drag
pipes in the midrange. Since the midrange is where the vast majority of normal driving occurs, it makes this system ideal for the street.
Gearing
• Gearing depends on the total weight of the machine and rider’s, the size of the engine, cams, exhaust system and type of riding to be done. Most
high performance engines, and particularly those with larger displacements, are capable of pulling more gear. We suggest you break the engine
in with stock gearing to minimize the load on the engine. After the engine is broken in you will have a better feel of its potential and can change
gearing accordingly.
• For those who wish to determine their final drive gear ratio, refer to the formula shown below:
Ratio is engine revolutions per one (1) rear wheel revolution.
Ratio =
(Clutch Sprocket*) X (Rear Wheel Sprocket*)
(Motor Sprocket*) X (Transmission Sprocket*)
*number of teeth on each sprocket
Compression
• Generally speaking, 1984 and later engines with the proper camshaft selection can operate using higher compression ratios with fewer problems
than their earlier counterparts. Keep in mind, though, that while engines with higher compression ratios make more horsepower and perform
better, they also tend to lose that performance edge faster, require more maintenance and start harder. As a rule, we prefer to limit the compression
ratio to no greater than about 10 to 1 for engine combinations used in normal street operation. A word of caution is in order. ­­Before building an
engine you may regret later on, carefully consider your riding needs, riding style and overall performance objectives.
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