S&S Cycle Super E and G Series Shorty Performance Carburetors for 1936-84 Harley-Davidson Big Twins and 1957-85 Ironhead Sportster Models - Manual (Page 12)

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normal riding conditions. The intermediate system
controls fuel delivery from just off idle to approximately
2500-3000 rpm or 55 to 60 mph depending on gearing.
Close attention must be paid when selecting
intermediate jet to achieve optimum performance and
best gas mileage. Intermediate jet (See Picture 22)
is reached by removing float bowl assembly. Size of
metering hole in intermediate jet is stamped in
thousandths of an inch on end or side of jet. Size of
intermediate jet installed in new carburetor from S&S® is
indicated on tag attached to carb or on printed label on
carburetor packing box. Keep this information handy for
future reference, especially when contacting S&S
Technical Services Dept. for assistance. It is a good idea
to record any jetting changes for future reference.
Picture
22
Intermediate Jetting Procedure:
1- Ride motorcycle several miles to bring engine up to
normal operating temperature.
2- Check idle mixture adjustment to be sure setting is
correct with fully hot engine. Shut off accelerator
pump by turning adjusting screw clockwise until it
stops. Do not force the screw.
3- Check throttling characteristics by slowly rolling
throttle on from a steady speed. This should be done
at rpm levels of approximately 2000, 2500, and 3000
rpm. (Depending upon gearing, vehicle speeds will
usually be between 30 and 60 MPH). "Popping" or
"spitting" (backfiring) in air cleaner indicates lean
condition requiring that intermediate jet be changed
to next larger size (size is stamped on end or side of
jet).
4- Change jet accordingly, adjust mixture screw and
repeat road test. Smallest intermediate jet that
eliminates this condition should provide best gas
mileage.
INTERMEDIATE SYSTEM NOTES:
• We recommend that you shut off accelerator pump while
fine-tuning intermediate circuit as fuel supplied by pump
can mask jetting symptoms. Consult "Accelerator Pump"
section of instructions.
• Whenever intermediate jet is changed, idle mixture screw
must be readjusted.
• Elevation changes: A simple readjustment of idle mixture
screw will often compensate for changes in elevation of
several thousand feet. S&S test riders have ridden through
changes upwards of 7000 feet without changing jets. In
other cases, and depending upon accuracy of initial jetting,
a change in intermediate and/or main jet may be required.
• Lower air density at higher elevation makes engine run
richer, meaning that smaller jets may be required to correct
overly rich condition. Lower elevation, nearer sea level,
makes engine leaner so larger jets may be required. While
rich condition can cause fouled spark plugs and poor
performance, lean condition can result in engine damage.
If smaller jets are installed for higher elevation, remember
to install larger jets for operation at lower elevation.
• Intermediate jet provides majority of fuel under average
operating conditions. While it is tempting to change main
jet because it is more accessible, in most cases intermediate
jet
should be changed to properly address
elevation/altitude-related problem.
D- Adjusting High Speed Circuit or Main Jet - High speed
circuit begins around 2500-3000 rpm or 55-60 mph
under steady speed conditions, and operates to
maximum attainable speed. High speed circuit will be
pulled in at much lower rpm if throttle is cracked open.
Main jet size is best determined by testing at drag strip or
dynamometer because maximum miles per hour, rpm
and horsepower are most reliable indicators of correct
jetting. Main jet (See Picture 23)is reached by removing
bowl plug. (See Jetting Chart Page XX).
Picture
23
High Speed (Main) Jetting Procedure:
1- Drag strip/dynamometer procedure
a- Sufficiently warm engine to begin testing.
b- Make run noting engine rpm and final speed or
horsepower.
c- Richen main jet by increasing jet size .004" and
make second run. Again, note rpm and final speed