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S&S Cycle Bore Big Twin Stroker Kit 1936–1999 3 7/16 - 3 1/2 User Manual

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Excessive material removed from frame may cause structural damage and possible failure resulting in personal injury to you or others
near you.

C. Install engine head mount.

NOTE: Stock head mount will be short if you are installing S&S® stroker kit with cylinder base plates thicker than .0625" (1⁄16"). If 1⁄16" thick or less plates are
used, modify stock mount. If plates thicker than 1⁄16" are used, install S&S heavy duty head mount, PN 93-4054. This mount is heavy duty and designed
especially to provide support for tall, big inch engines. Its two piece design permits precise head to frame alignment which reduces stress and potential
head mount failure.

Improper mounting of engine in frame may cause engine to come loose resulting in damage and/or failure of engine motor mounts and/
or other engine mounting brackets.

5. Timing, Carburetion, Exhaust, Gearing and Break-in (All Engines)

Ignition Timing Notes

See Step 3, “Lower End Assembly” page 5, for explanation of S&S timing marks.

S&S flywheels have timing marks that position pistons at 35° before top center, same as stock, when mark is in center of timing hole. Placing mark to
right side of hole or just entering hole advances timing almost 5°. Vice versa, if mark is just leaving hole, timing is retarded almost 5°.

Maximum performance in early engines traditionally has been with timing set at 37° to 39°, but because of poor gasoline, detonation, etc. it is advisable
to stay with 35°. Some builders will even retard ignition timing slightly because of aforementioned problems, but if you do, watch heat build-up If there
is any doubt, stay with H-D® factory recommended settings. Tests of S&S Sidewinder® kits in Evolution™ engines conducted on our dyno have indicated
that the best horsepower will be produced with timing set from 30° to 35°, depending on cylinder head design, compression ratio and type of fuel.

Whatever ignition system is used, the best rule of thumb for most situations is to follow stock timing specs and watch for signs of detonation and/or
excessive heat.

Ignition timing for engines with dual plugged heads should generally be retarded 5-8° from the stock setting. However, due to the large number of
variables involved, optimum ignition timing is impossible to accurately predict and must be determined for each engine by experimentation.

Improper ignition timing may cause excessive engine heat which may damage pistons and/or other engine components.

Carburetion Notes

All S&S test engines have been run with S&S carburetors. A Super E or Super G carburetor is recommended for most strokers. Consult carburetor jetting
instructions for specific jetting recommendations.

If another type carburetor is used, it must be made to run rich enough so engine is not damaged. Other carburetor types are a personal problem and we
cannot answer questions concerning them. It is best to call carb manufacturer if you have any questions.

Exhaust Systems Notes
• To establish performance guidelines, S&S used 30" long stock diameter drag pipes on knucklehead, panhead and shovelhead engines with good

results. We suggest you try them on these engines to establish a baseline to compare with other systems. Evolution engines are easier to carburate
with muffled systems.

• You might ask the manufacturer of the exhaust system you are considering if he has had any experience with S&S strokers. Many systems are made for

looks with little consideration given to performance. Most stock systems and many aftermarket ones tried are too restrictive for good performance. S&S
does offer a series of mufflers that can be used with stock header pipes. These work very well in most situations and offer an inexpensive alternative to a
new exhaust system.

Gearing Note

Gearing depends on total weight of machine and rider(s), size of engine, caming, exhaust system and type of riding to be done. Most strokers are
capable of pulling more gear. We suggest you break engine in with stock gearing to minimize lugging engine. After 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 the formula is as follows:

Engine Revolutions Per One Revolution of Rear Wheel=

(Clutch Sprocket*) x (Rear Wheel Sprocket*)

(Motor Sprocket*) x (Transmission Sprocket*)

* Number or teeth on each sprocket

WARNING

CAUTION

CAUTION