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 13)

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or horsepower.
d- Continue procedure until mph/horsepower falls
off.
e- Decrease or lean main jet size by .002" to gain
best rpm and mph. When making runs on drag
strip, strive for consistent miles per hour, not
lowest ET.
2- Street Procedure - S&S uses "rpm" method to
determine main jet size. Under racing conditions this
level is where horsepower peaks and begins to taper
off and is where gear shifts occur. Main jet that
makes engine accelerate strongest or rpm through
gears quickest is correct.
NOTE: Placing engine under load by accelerating uphill may make
result of jet change more pronounced and easier to interpret.
a- Warm engine to operating temperature.
b- Accelerate rapidly through gears noting how
quickly and smoothly engine reaches rpm level
where pull of engine begins to fade and gear shift
occurs.
c- If engine backfires in carburetor and sputters or
"breaks up"and/or dies during acceleration,
increase or richen main jet size .004" larger and
road test again. Note engine smoothness and how
easily engine reaches rpm where gear shift occurs.
d- If engine runs flat and sluggish or "blubbers" or
will not take throttle, decrease or lean main jet
size .004" smaller and road test again. Note
engine smoothness and how easily engine
reaches rpm where gear shift occurs.
e- Continue changing main jets until jet which
makes engine accelerate or rpm through gears
quickest and smoothest is identified. S&S's®
experience is that jetting about .006" smaller
(leaner) than correct will make engine break up
and quit. Jetting about .006" larger (richer) will
make engine blubber and miss.
NOTES:
• Correct carb jetting is essential for optimum performance
on street, strip and dynamometer. Other common causes
of poor performance in modified engine are inappropriate
exhaust and incorrect ignition timing.
• S&S special main jet tool is extremely handy for changing
main jets. Try it, you'll like it!
E- Troubleshooting Tips for Intermediate and High Speeds
Engine will not run at steady speed or rpm or quits for no
apparent reason:
1- Restriction in fuel supply system - Gas tank vent
plugged, needle and seat not working properly (See
"General Information"), gas petcock too small, or
defective vacuum petcock. Stock petcock is generally
adequate, but may require running on reserve to
provide sufficient fuel for big inch engines. If fuel
delivery to carb is questionable, S&S recommends an
aftermarket high flow petcock.
2- Faulty ignition/electrical system - Fouled plugs, worn
points or condenser, defective coil or solid state
module, improper ignition timing, loose wire, faulty
circuit
breaker or ignition switch. Many
ignition/electrical problems occur repeatedly at same
rpm because of vibration specific to that rpm.
3- Incorrect intermediate and/or high speed jetting. See
"Adjusting Carb - Intermediate System" and "High
Speed Circuit or Main Jet."
4- Foreign material in air or gas passageway in carb
causing flow restriction. Picture 24shows
intermediate air bleed metering hole. Picture 25.
shows main discharge air bleed metering jet. Use
compressed air to clear holes
Picture
24
Picture
25
.
Do not use wire or drill to clear hole in carb bowl. If size of
hole is altered, starting system will be altered and carburetor
bowl irreversibly damaged.
Compressed air and particles dislodged by compressed air are
potentially harmful to eyes and body. Wear protective
goggles when using compressed air and always direct air
stream away from yourself and others nearby.