S&S Cycle Forged Pistons For Stock Bore And 35/8 Bore Harley-Davidson 1936-99 Big Twin And 1957- Present Sportster Models - Manual (Page 4)

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4. Repeat this procedure 3 or 4 times. Each successive time it should
take slightly longer to warm up and you can increase the temp
slightly each time (+10°). You can be more liberal each time with
the rpm, gently vary rpm continuously from idle up to 2500 rpm
in the final cycle. Don’t be too concerned with final carb settings
at this time because idle speed and mixture cannot be correctly
set until the motor reaches full operating temperature. The motor
should not reach that temperature during these cycles. Do not
allow engine temperature to become excessive. After the motor has
cooled to room temperature for the final time you are ready to start
the 500 mile engine break-in process.
5. The first 50 miles are most critical for new rings and piston break-in.
Engine damage is most likely to occur during this period. Keep heat
down by not exceeding 2500 rpm. Avoid lugging the motor, riding
in hot weather or in traffic. Vary the engine speed. Do not lug the
engine. We recommend changing the oil at 50 miles.
6. The next 500 miles should be spent running engine no faster than
3500 rpm or 60 mph. Avoid continuous steady speeds, and do not
lug the engine. Vary engine rpm. We recommend changing the oil
again at 500 miles.
CAUTION
Lugging or running engine prematurely at sustained high rpm
may result in damage to pistons and other engine components.
S&S® voids its guarantee if engine is not broken in properly.
7. For the balance of the first 1000 miles the motor can be run in a
normal but conservative manner. You can be more liberal with the
rpm range and motorcycle can be operated at normal highway
speeds. Avoid overheating or putting any hard strain on the engine:
no drag racing, dyno runs, excessive speed, trailer towing or sidecar
operation.
8. After 1000 miles, verify carburetor jetting and adjustment. Change
the engine oil. Motorcycle can now be operated normally.
9. Have Fun!