Caution warning – S&S Cycle Super B Series Carburetor User Manual
Page 8
Main jet size is best determined by testing at drag strip, because
maximum miles per hour and rpm are best indicators of actual
horsepower engine is developing. S&S
®
recommends that high
speed jetting be done at drag strip.
Dragstrip Procedure
1.
Warm up engine enough to begin testing.
2.
Make run noting engine rpm and final speed.
3.
Increase or richen main jet size .004 larger and make second
run. Again, note rpm and final speed.
4.
Continue procedure until mph falls off.
5.
Decrease or lean main jet size by .002 to gain best
(maximum) rpm and mph. When making runs, do not strive
for ET’s but for consistent miles per hour.
Street Procedure
S&S uses what we call “RPMing” method to determine correct
main jet size. Hard acceleration is evaluated up to the rpm where
horsepower peaks and begins to taper off and gear shift occurs.
Main jet that makes engine accelerate strongest or rpm through
gears quickest is correct.
1.
Warm engine to operating temperature.
2.
Accelerate rapidly through gears noting how quickly and
smoothly engine reaches rpm level where pull of engine
begins to fade and gear shift occurs.
3.
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 level where
gear shift occurs.
4.
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 level where gear shift occurs.
5.
Continue changing main jets until one is selected that makes
engine accelerate or rpm through gears most quickly and
smoothly. Our experience has taught us that a jet about .006
smaller (leaner) than correct one will make engine “break
up” and quit. A jet about .006 larger (richer) will make
engine “blubber” and miss.
Troubleshooting Tips for Intermediate & High Speeds -
Engine will not run at steady speed or rpm:
1.
Restriction in fuel supply system - gas tank vent plugged,
stock gas petcock too small.
2.
Faulty ignition system - fouled plugs, worn points, defective
coil or solid state module, improper ignition timing.
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 and/or gas passageway in carb
causing flow restriction. Clear holes with forced air.
Do not use wires or drills to clear holes. If sizes are altered,
air/fuel ratios of idle and intermediate systems will be
changed resulting in poor performance and irreversible
damage to carburetor body and intermediate jet.
Compressed air and particles dislodged using compressed air
are harmful to eyes and body. Wear protective goggles
when using compressed air and always direct air stream
away from body parts such as hands and eyes and other
people near you.
5.
No air cleaner used or air cleaner used is brand other than
S&S. Some air cleaner designs restrict air flow so that carb
cannot draw air freely as needed. Also, other air cleaners
may obstruct bowl vent hole on inlet end of carb and change
bowl air pressure.
NOTE - Bowl vent hole passageway leads to cavity above fuel in
bowl and is designed to equalize bowl pressure and atmospheric
pressure. If high or low bowl pressure relative to atmospheric
pressure develops, engine may run erratically.
6.
Air horn used without shrouding bowl vent on end of
carburetor body.
NOTE - Bowl vent should be shrouded to insure uniform
atmospheric air pressure between cavity above fuel level in
bowl and area outside carburetor body. If high or low bowl
pressure relative to atmospheric pressure develops, engine may
run erratically.
7.
Valve train defect - bad valves, sticky valves, bad or broken
springs, improper clearances for high lift cam or, defective
camshaft with improper valve timing.
8
CAUTION
WARNING
Figure B
Figure C
1
2
3
Arrow 1: Throttle plate horizontal.
Arrow 2: Throttle arm against stop.
Arrow 3: Throttle arm set screw.
Bevels must be at angles shown by arrows
when installing plate.