S&S Cycle Replaceable Main Air Bleed for all S&S Super E and G Carburetors - Manual

1
Instruction Sheet Addendum
to Instruction 51-1012
04-05-04
Copyright®, 2004
by S&S Cycle, Inc.
All rights reserved. Printed in the U.S.A.
Because every industry has a leader
S&S Cycle, Inc.
14025 County Highway G Box 215
Viola, Wisconsin 54664
Phone: 608-627-2080 • Fax: 608-627-1488
Technical Service Phone: 608-627-TECH (8324)
Technical Service Email: [email protected]
Website: www.sscycle.com
The main air bleed passage in S&S Super "E" and
"G" carburetors produced for the 2004 model year
and later is fitted with a replaceable .040” jet in place
of the .040" drilled main air bleed passage. The
replaceable jet allows changing the size of the main
air bleed. Carburetors with this modification can be
identified by a serial number that begins with the
letter E or higher.
The .040" diameter main air bleed hole was and
continues to be the standard size on all S&S "E"& "G"
carburetors. The purpose of the main air bleed is to
provide a vacuum signal to the main fuel circuit. This
vacuum signal determines the rpm point where the
carburetor transitions from running on the
intermediate jet and begins to draw fuel through the
main jet.
The standard .040" diameter air bleed is the optimum
size for most engine combinations, and should not be
changed under most circumstances, regardless of
intermediate and main jet selections.
The option of changing the size of the main air bleed
allows tuners to address midrange rpm driveability
problems caused by poorly performing exhaust
systems, such as unbaffled drag pipes. Radical cams
can also increase the difficulty of tuning some
exhaust systems.
An exhaust pipe that is not correct for the engine will
have reversion pulses that interfere with the
cylinder’s ability to fill in the mid rpm range just at the
time the main jet is coming in.
One way to improve the midrange rpm operation of
an engine that runs rich in the midrange, is to enlarge
the main air bleed.
Before the replaceable main air bleed was
introduced, the main air bleed was enlarged by
drilling to a larger size. Now, the air bleed size can be
enlarged simply by changing the jet.
Enlarging the main air bleed hole decreases the
vacuum signal to the main jet. Because of this, the
engine has to reach a higher rpm to create enough
vacuum to overcome the increased air bleed size and
draw fuel through the main jet. This keeps the
carburetor running on the intermediate jet to a higher
rpm, and delays the start of main jet operation.
For tuning the main air bleed, S&S recommends an
initial increase from the standard .040" jet to an .048"
jet as a starting point. Available jets and part numbers
are listed in the S&S catalog.
NOTES:
● Changing the main air bleed size should be done
only after determining a mid range driveability
problem cannot be corrected by changing the
intermediate and main jets.
● It is never necessary to reduce the size of the main
air bleed below .040".
● Shifting the start of main jet operation to a point
higher up the rpm scale can lessen the effects of
mid rpm driveability problems caused by
mismatched cam and exhaust systems, but will not
allow the engine to perform as well as it would with
a well designed exhaust system.
Replaceable Main Air Bleed for all S&S Super "E" and "G" Carburetors
.040 replaceable main air bleed.
All "E" & "G" with serial number
starting with E or higher. .040 drilled main air bleed. All
"E" & "G" with serial number
starting with D or lower.