Caution – S&S Cycle Performance Replacement Cylinder Head Kit for 1984-99 Big Twin Engines and Harley-Davidson Sportster Models User Manual

Page 5

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 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 Stock replacement 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 Stock replacement heads on big twins showed that best performance was achieved with the
ignition timing set at; 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