S&S Cycle Replacement Cylinder Heads for 1984-1999 Harley-Davidson Evolution Engines and 1986-2003 Sportster Motorcycles User Manual

Page 8

Installation of threadsert where it protrudes above air
cleaner backplate mounting boss surface may damage air
cleaner backplate.

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.

NOTE: Throttle must not bind and must snap shut to fully closed
position when released.

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.

NOTE: Fuel needle and seat assembly must completely shut off
fuel supply entering bowl. Fuel line connections must not leak.

Unwarranted gasoline leaking by fuel inlet needle may flood
engine causing damage to components.

Unwarranted gasoline leaks at fuel line connections and/or
past inlet needle may flood engine and overflow on
surrounding area creating fire hazard.

Engine Break-In Procedure

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 big twin 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.

Do not allow engine temperature to become excessive as
permanent engine damage may result.

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.

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.

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.

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.

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).

2000 miles and up—have fun!

Performance Notes

Ignition Systems
●

Stock electronic ignition systems are satisfactory, but
usually will not allow modified engines to realize their full
potential. The S&S Intelligent Spark Ignition system (IST)
provides optimum ignition timing for any engine and
works in all but turbocharged and supercharged
applications. It learns about the engine it is installed on,
automatically senses the beginnings of spark knock, and
sets the advance curve and total advance for maximum
performance under all conditions. If not using an S&S
ignition, a point type ignition system or an aftermarket
high performance electronic unit is recommended. This
allows flexibility in engine timing not possible with stock
ignition systems.

●

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 have timing marks that when
located in the center of the timing hole position the pistons
in the same location before top center as stock Harley-
Davidson

flywheels. Placing the mark to the right side of

the hole or just entering the hole advances timing almost
5°. Vice versa, if the mark is just leaving the hole, timing is
retarded almost 5°.

●

Timing - Tests conducted using S&S Super Stock

heads on

big twins and Harley- Davidson

Sportster

models showed

that best performance was achieved with the ignition
timing set at; 4" bore engines 28°-30° total advance, 3

⁄

and 3

⁄

" bore 30°-32° total advance.

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.

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

CAUTION

WARNING

CAUTION

WARNING

CAUTION