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Set both the high and low speed screws from lightly seated to 1 1/4 turns out. This will give you a rough setting that will allow the saw to start and idle. Set the idle screw to where the chain just stops moving at idle.

With the saw warmed up adjust the low speed screw out until the saw smokes a bit and acceleration is sluggish. Bring the screw in small steps until the hesitation is gone from the acceleration…you may need to adjust the idle again after this.

Now hold the throttle wide open and while it is wide open adjust the high speed screw in until the noise becomes smooth and the saw “sings”. Do not leave it at this setting as it will burn down in short order. Once the saw is singing back the screw out until you can hear the saw’s tone “roughen”….then back the screw out a tad more for good power / fuel under load.

That’s it in a nutshell…here’s a good link also…

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Turn the idle screw — I — clockwise until the chain starts to spin, then turn it counterclockwise slightly. Adjust the screw to find the highest setting possible without making the chain spin. Check the setting by holding a digital tachometer over the spark plug. It should read between 2,700 and 2,900 rpm.
Run the engine for five minutes at half throttle to bring it to its operating temperature. Then, turn the idle mixture screw slowly clockwise until the engine begins to slow. Turn the screw in the opposite direction until the engine again begins to slow. Finally, turn the screw back to the midpoint.
If the carburetor is new or has been rebuilt, you should set it to “factory” adjustment. You can do so by adjusting the idle mixture screws to 1.5-2 turns out, and the idle speed screw to 1-1.5 turns in. Warm the Engine Up. The engine`s running temperature directly correlates with proper air and fuel mixtures.
Find the adjustment screws on the front of the carburetor.

There should be two screws on the front of the carburetor, which are used to adjust the air and fuel mixture. These often look like flat-head screws, and you can use a screwdriver to turn them, adjusting the amount of fuel and air mixing in the carb.

When adjusting the air screw, if you want to go leaner then you need to open it up to allow more air in. Turn it out (counterclockwise). To make it run richer, turn it in (clockwise) to decrease the amount of air allowed through it.
The throttle controls how much air is allowed to flow through the carburetor, and the flow of air is what controls how much fuel is also fed into the engine. The Venturi Principle/Effect states that when air flows through a restriction of a tube (narrowing), the air speed increases, and air pressure decreases.
Tip: The factory position for most air fuel mixture screws is usually between 1.5 and 2.5 turns out from being screwed all the way in. If you ever want to start fresh, turn the screw clockwise until it is lightly seated, then back it out about 2 turns.
Optimum Air/Fuel Ratio

For peak power, most engines like an air/fuel ratio of 12.8 to 13.2. If you can tune a carb to deliver a consistent A/F within this range, the engine will usually run at its full potential from off-idle to wide open throttle.

Typically, there`s a 12:1 or 15:1 ratio of air to fuel, and when there`s too much air or not enough fuel, it causes sneezing or popping sounds in the intake.
This method involves looking at the base of the spark plug insulator (white part of the plug) for a slight coloring on the insulator just above where the insulator comes through the steel case. If the mixture is too lean, it will leave no color, while a rich mixture will cause the fuel ring to become more prominent.
There should be two screws on the front of the carburetor, which are used to adjust the air and fuel mixture. These often look like flat-head screws, and you can use a screwdriver to turn them, adjusting the amount of fuel and air mixing in the carb.
Required fuel pressure can vary depending on your vehicle`s engine and fuel system. Carbureted engines may require as little as 28 kPa (4 PSI), while modern multipoint fuel injected high-performance engines can require as much as 414 kPa (60 PSI).

Discover Relevant Questions and Answers for Your Specific Issue

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Carb screws need adjusted i need to know the settings
ANSWER : Hi. Lightly seat the low screw and bring it out one and a quarter turns. Lightly seat the high and bring it out one turn. Adjust idle screw to suit. Regards Phil.

Read Full Q/A … : McCulloch

1 Solution for ”B320 leaf Blower starts idles fine but when you move lever to full throttle it bogs like a sick cat I have cleaned and completly rebuilt the carbB320 and it still does the same exact thing The carb might as well have no carb adjustement screw for it does not make any difference where it is turned for it makes no change In fact the screw will only turn a part of a turn it could not be removed to clean it out for some reason it will only move a little Has anybody else had similar problems with these Walbro carbs And by the way is there a adjusting tool out there that might work better than a ground down 3/16 nut driver for it has limited sp”
ANSWER : That adjustment is a cap the real screw is under that cap/1/4 turn thing.u need to pop it off or drill it out to get to the real screw. its a safety thing so as not to run it to lean and burn up the motor. lean it out a little at a time, i mean a little like 1/16 of a turn, test and adjust again if needed.

Read Full Q/A … : McCulloch

Need to know what the carb adjustments are for a model 61 husky
ANSWER : Low side one turn out from bottem.high sie is the same.after saw is running readjust both high and low.make sure the side dosen’t go in any more then 3/4 of a turn out……if it does you will burn up the saw….

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How to adjust a carbretor how to set the jets on a 670 super champ
ANSWER : I’d suggest removing all idols then re-inserting evenly(about 3-4 full turns each to start)/or screw them all the way in and work backwards,then while engine is running tweak them (again evenly) until the engine runs at about 1250rpm without throttle or choke. basically as long as all 4 carbs are set identically and the revs are good your done.this videos of a dodge but its the same principle

Read Full Q/A … : McCulloch

Adjust high low screws on carb.
ANSWER : I found one at my local parts store (they also work on them) for $5. It looks like a screwdriver with a special tip on it………

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What tool is required to adjust the carb. on a 142e husquvarna chainsaw?
ANSWER : Http://

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Trimmer takes a long time to warm up. Cuts out when under full trottle and will not idle. Which screws are high and low speed adjust? There are two of them side by side. Do U need a special tool to adjust hi/lo speed screws?
ANSWER : Sounds like the carb needs cleaning, it is staying on choke to long. I would not bother the screws, or either a hose for the gas flow is bad.

Read Full Q/A … : McCulloch

How do you get to the throttle jets huskvarna 130BT blower
ANSWER : The 130 has a rotary style carb, so the only adjustment is down through the top of the throttle spindle, you will need a very small flat blade screw driver, the screw down here will lift or raise the needle in the carb, there may well be a plastic plug to remove before you can get deep enough to adjust it.

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