Base line Settings
Base line Settings
Speed Screw 1 to 1 1/2 turns
Mixture Screw 2 turns
Your settings with
engine running
Speed Screw______________
Mixture Screw______________
It
is most important to verify all linkage and levers are installed without
binding and the linkage opens to full throttle position and is allowed to
close to the Idle Speed Screw. This is the number one and two reasons for
tuning errors, improper linkage installations and over tightened linkage nut,
causing binding in the linkage assembly.
CALIBRATIONS
MAY VARY DUE TO REGIONAL FUELS AND STATE OF ENGINE TUNE AND PERFORMANCE. POOR RUNNING
QUALITY DOES NOT MEAN YOU HAVE A CARBURETION PROBLEM. THE ADVANTAGE OF THE
WEBER CARBURETOR IS ITS EASE OF ADJUSTMENT AND TUNING.
“LEAN
BEST IDLE” Procedures
After
confirming the linkage allows the throttle to seat against the Idle Speed
Screw. Back off the Idle Speed Screw until it doesn’t touch the throttle
lever. Turn the Speed Screw in until it contacts the throttle lever and turn
it in 1 ½ turns. Repeat this with the other carburetor. Turn the Mixture
Screw in until it “LIGHTLY” seats, then back out the screw 2 full turns.
a.
Start the engine, it will run slow and like a tractor. As long as it will
stay running, the idle speed is not important at this point.
b.
First, turn in each mixture screw until the engine runs worse, then back out
the screw ¼ turn at a time. The engine should start to smooth out. Continue
to back each screw ¼ turn at a time until the screw does nothing or runs
worse. Then turn it back in to the point where it ran best. You want to tune
the engine by sound. Adjust each mixture screw to the best, fastest and
smoothest running point. Do this procedure with each mixture screw.
c.
Now you may adjust the Idle Speed Screw. It should be sensitive and only
“require” ½ turn out to lower the idle speed. The Speed Screw should never be
in more than 1 ½ turns in.
d.
These carbs are commonly used in pairs, this makes the synchronization
important, be sure to bring the high flowing carb down to the low flow carb.
Then bring them both up to “proper” Idle speed. The Idle Speed Screws are
never opened more than 1½ turn in maximum.
e.
After synchronizing multiple carbs, reconfirm steps b. c. & d.
Pump
By-pass Valve:
The
pump by-pass valve is designed to allow fuel into the pump circuit and when
depressed, by-pass a percentage of the fuel delivered to the accelerator
pump nozzle/jets. (by-pass through a hole on the side of the valve back into
the fuel bowl). We have included the zero by-pass valve. (no hole in the
side) This will deliver all of the available fuel to the engine and not
by-pass back into the fuel bowl. This will increase the duration and fuel
volume of the pump shot with the original pump nozzle/jets. The accelerator
pump by-pass valve is located in the bottom of the fuel bowl. One is required
per carburetor.
Simple
Rules for low speed calibration
If
the mixture screw is more than 2 1/2 turns out turns then the Idle jet is too
lean (too Small). When the mixture screw is less than 1 1/2 then the Idle jet
is too rich (too large). These assumptions are based on the fact that the
speed screw setting is not opened more than 1 1/2 turns. If the speed
screw has to be opened 2 or more turns then this is also an indication of a
lean condition usually requiring greater change. At times it may appear to be
showing signs of richness or flooding it is really a lean condition. See
pictures and notes in the tech 2 article supplied in the kit instructions,
view and please understand the need to keep throttle plate as near to closed
as possible so as not to prematurely expose the transition holes. This is
what causes the visible rich condition, and confirms the need to increase the
jet size. JET KITS are available if needed.
EXAMPLE
With the speed screw set at no more than one half (1 1/2) turns in after
contact with the stop lever; and the best idle occurring with the mixture
screw set at 3 turns from bottom, indicates the need for a larger Idle
jet. Achieving the best idle at under 2 turns indicates the need for a
smaller idle jet.
The
secret to understanding the critical nature of the carburetor set up and the
advantages of a WEBER over other carburetors is the Idle circuit. Referred to
as the low speed circuit by Weber, this circuit is responsible for 80% of the
driving operation. This is the reason that the Weber should give a fuel
economy improvement over most factory carbs along with significant
performance gains. In the worst case you should not see a significant fuel
economy loss over stock, while improving HP & Drivability.
The
Weber Carburetor is a sequentially timed device to the motor like the
distributor. Time taken in the setup will provide more fun later.
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Base line Settings Speed Screw 1 to 1 1/2 turns Mixture Screw 2 turns Your settings with engine running Speed Screw______________ Mixture Screw______________ |
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It is most important to verify all linkage and levers are installed without binding and the linkage opens to full throttle position and is allowed to close to the Idle Speed Screw. This is the number one and two reasons for tuning errors, improper linkage installations and over tightened linkage nut, causing binding in the linkage assembly.
CALIBRATIONS MAY VARY DUE TO REGIONAL FUELS AND STATE OF ENGINE TUNE AND PERFORMANCE. POOR RUNNING QUALITY DOES NOT MEAN YOU HAVE A CARBURETION PROBLEM. THE ADVANTAGE OF THE WEBER CARBURETOR IS ITS EASE OF ADJUSTMENT AND TUNING.
“LEAN BEST IDLE” Procedures After confirming the linkage allows the throttle to seat against the Idle Speed Screw. Back off the Idle Speed Screw until it doesn’t touch the throttle lever. Turn the Speed Screw in until it contacts the throttle lever and turn it in 1 ½ turns. Repeat this with the other carburetor. Turn the Mixture Screw in until it “LIGHTLY” seats, then back out the screw 2 full turns. a. Start the engine, it will run slow and like a tractor. As long as it will stay running, the idle speed is not important at this point. b. First, turn in each mixture screw until the engine runs worse, then back out the screw ¼ turn at a time. The engine should start to smooth out. Continue to back each screw ¼ turn at a time until the screw does nothing or runs worse. Then turn it back in to the point where it ran best. You want to tune the engine by sound. Adjust each mixture screw to the best, fastest and smoothest running point. Do this procedure with each mixture screw. c. Now you may adjust the Idle Speed Screw. It should be sensitive and only “require” ½ turn out to lower the idle speed. The Speed Screw should never be in more than 1 ½ turns in. d. These carbs are commonly used in pairs, this makes the synchronization important, be sure to bring the high flowing carb down to the low flow carb. Then bring them both up to “proper” Idle speed. The Idle Speed Screws are never opened more than 1½ turn in maximum. e.
After synchronizing multiple carbs, reconfirm steps b. c. & d. Pump By-pass Valve: The pump by-pass valve is designed to allow fuel into the pump circuit and when depressed, by-pass a percentage of the fuel delivered to the accelerator pump nozzle/jets. (by-pass through a hole on the side of the valve back into the fuel bowl). We have included the zero by-pass valve. (no hole in the side) This will deliver all of the available fuel to the engine and not by-pass back into the fuel bowl. This will increase the duration and fuel volume of the pump shot with the original pump nozzle/jets. The accelerator pump by-pass valve is located in the bottom of the fuel bowl. One is required per carburetor. |
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Simple Rules for low speed calibration If
the mixture screw is more than 2 1/2 turns out turns then the Idle jet is too
lean (too Small). When the mixture screw is less than 1 1/2 then the Idle jet
is too rich (too large). These assumptions are based on the fact that the
speed screw setting is not opened more than 1 1/2 turns. If the speed
screw has to be opened 2 or more turns then this is also an indication of a
lean condition usually requiring greater change. At times it may appear to be
showing signs of richness or flooding it is really a lean condition. See
pictures and notes in the tech 2 article supplied in the kit instructions,
view and please understand the need to keep throttle plate as near to closed
as possible so as not to prematurely expose the transition holes. This is
what causes the visible rich condition, and confirms the need to increase the
jet size. JET KITS are available if needed. EXAMPLE With the speed screw set at no more than one half (1 1/2) turns in after contact with the stop lever; and the best idle occurring with the mixture screw set at 3 turns from bottom, indicates the need for a larger Idle jet. Achieving the best idle at under 2 turns indicates the need for a smaller idle jet. The secret to understanding the critical nature of the carburetor set up and the advantages of a WEBER over other carburetors is the Idle circuit. Referred to as the low speed circuit by Weber, this circuit is responsible for 80% of the driving operation. This is the reason that the Weber should give a fuel economy improvement over most factory carbs along with significant performance gains. In the worst case you should not see a significant fuel economy loss over stock, while improving HP & Drivability. The Weber Carburetor is a sequentially timed device to the motor like the distributor. Time taken in the setup will provide more fun later. |
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