S&S Cycle Piston and Cylinder Kits for all 1986-up Harley-Davidson Sportster Models - Manual (Page 4)

a. Initial start up. Run engine approximately one minute at
1250-1750 rpm. DO NOT crack throttle or subject to any loads
during this period as head gaskets are susceptible to failure
at this time. During this time check to see that oil pressure is
normal, that oil is returning to the oil tank, and that no leaks
exist.
b. Shut off engine and thoroughly check for any leaks or other
problems. Let engine cool to the touch
c. After engine has cooled, start up again and allow the motor
to build some heat. Engine should be run no longer than
three to four minutes. When the cylinders become warm/hot
to the touch (approximately 150°) shut the motor down and
let it cool to room temp. Follow the same cautions as for the
initial start-up, and continue to watch for problems.
d. 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 1000-mile engine break-in process.
e. 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 engine, riding in hot weather, or in stop and go
traffic. Vary the engine speed, but do not lug the engine. We
recommend changing the oil at 50 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.
f. 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.
g. 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.
h. After 1000 miles, verify carburetor jetting and adjustment.
Change the engine oil. Motorcycle can now be operated
normally.
i. Have Fun!
Additional Information:
The following information is provided in case pistons must be
replaced as in the event of an engine overhaul, or if the engine is
to be set up for immediate severe duty such as drag racing or other
competition application. See Piston Fit Specification chart below.
1. For maximum piston and ring life, fit pistons using close fit
dimensions. Close fit requires absolute adherence to new engine
break-in as described in Step 6.
2. For immediate drag strip use, fit pistons using loose fit dimensions.
Break in rings and pistons with 50 easy miles if possible. Piston
and ring life will be reduced with loose fit dimensions.
3. Measure all pistons at widest point across thrust face,
perpendicular to wristpin hole. Several measurements should be
taken to locate widest point. Typically, this will be at bottom of
piston skirt, and approximately 1⁄2" below level of wristpin hole.
4. S&S® recommends #220-#280 grit stone for final honing of S&S
bore cylinders.
5. Follow procedure recommended in Harley-Davidson® service
manual for boring and honing S&S cylinders, or follow instructions
included with S&S Cylinder Torque Plate Kit. Torque plates must
be used to simulate compressive stress in an assembled engine.
Cylinders will distort if torque plates are not used.
CAUTION
Failure to follow instructions and perform required clearancing,
installation and/or break-in procedures may result in damage
to pistons and/or other engine components not covered under
warranty.
4
EXPANDER GAP
FRONT PISTON
REAR PISTON
SECOND COMPRESSION
RING GAP
TOP RAIL GAP
BOTTOM RAIL GAP
TOP COMPRESSION
RING GAP
SECOND COMPRESSION
RING GAP
EXPANDER GAP
TOP RAIL GAP BOTTOM RAIL GAP
TOP COMPRESSION
RING GAP
Figure 5: GAP PLACEMENT ILLUSTRATION
PISTON FIT SPECIFICATIONS
PART #
DESCRIPTION CLOSE FIT LOOSE FIT
106-5548 – STD
106-5549 – +.010"
106-5550 – +.020"
883 TO 1200 CONVERSION PISTON
1986-UP XL 31⁄2" BORE DISHED
DOME
.0025" TO.0030" 0035" TO.0045"
920-0070
1250CC PISTON 1986-UP XL
39/16" BORE FLAT DOME
.0025" TO.0030" 0035" TO.0045"
920-0071
1250CC PISTON 1986-UP XL
39/16" BORE 5.5CC RAISED DOME
.0025" TO.0030" 0035" TO.0045"
*NOTE: FIT WRISTPINS AT .0007" TO .0014".