Mcculloch Mac 120 Manual

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The McCulloch Power Mac 310 chain saw is a somewhat vintage model. It was new about the same time the first personal computers came on the market, in the mid 1980s. Like most chain saws, it has three carburetor adjustment screws, and chances are good that they need adjusting. It's a fairly simple matter to set the idle and low-speed screws, but setting the high-speed screw is challenging and shouldn't be attempted without a tachometer. Without one, it's simple to set the fuel mixture too lean and burn out the motor.

1

Remove the air box cover from the left side of the McCulloch Power Mac 310 chain saw by using a Phillips screwdriver to remove its single screw. The chain saw's left side is the side that is on your left when you operate the chain saw. Remove the air filter, and clean it with compressed air. If you can't clean it, then replace it.

2

Mcculloch Mac 120 Manual

Drain fuel from the chain saw's fuel tank, and replace it with fresh, high-octane gasoline mixed with two-cycle engine oil at a ratio of 40 parts gasoline to 1 part oil. Fill the fuel tank completely with the mixture. Otherwise, the engine might run too rich the next time you fill the tank.

The McCulloch Power Mac 310 chain saw is a somewhat vintage model. It was new about the same time the first personal computers came on the market, in the mid 1980s. Like most chain saws, it has.

3

Start the chain saw's engine, and let it warm up for about five minutes. If the carburetor is so far out of adjustment that the engine won't start, turn both the high-speed screw -- H -- and low-speed screw -- L -- clockwise as far as they will go, using a flat-head screwdriver, then turn them counterclockwise by 1 1/2 turns.

4

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.

5

Turn the low-speed screw clockwise until the engine begins to race, and make a note of that position of the screw. Turn the low-speed screw counterclockwise until the engine begins to stall, and note that position of the screw. The final setting is midway between those two positions. This adjustment may throw off the idle adjustment, and so resetting it may be necessary.

6

Engage the throttle, and while the saw is running at full speed, turn the high-speed screw clockwise until the engine races and the motor sounds thin. Turn the high-speed screw counterclockwise until the motor takes on a lustier gurgling sound without losing power. Check the engine speed with the digital tachometer. It should be fewer than 13,000 rpm.

7

Readjust both the low-speed screw and idle screw.

Things You Will Need

Mcculloch Mac 120 Chainsaw Service Manual

  • Phillips screwdriver
  • Compressed air
  • New air filter (optional)
  • High-octane gasoline
  • Two-cycle engine oil
  • Flat-head screwdriver
  • Digital tachometer

Tip

  • The clutch should engage the saw's chain by the time the engine reaches a speed of 3,800 rpm.

Warning

  • Keep people and pets out of the area when making the adjustments because the chain may spin unexpectedly.

References (2)

About the Author

Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.

Photo Credits

Mcculloch Mac 120 Repair Manual

  • Hemera Technologies/Photos.com/Getty Images
Cite this Article
Choose Citation Style
Deziel, Chris. 'How to Adjust the Carburetor on a McCulloch Chain Saw Model 310.' Home Guides | SF Gate, http://homeguides.sfgate.com/adjust-carburetor-mcculloch-chain-saw-model-310-101690.html. Accessed 25 August 2019.
Deziel, Chris. (n.d.). How to Adjust the Carburetor on a McCulloch Chain Saw Model 310. Home Guides | SF Gate. Retrieved from http://homeguides.sfgate.com/adjust-carburetor-mcculloch-chain-saw-model-310-101690.html
Deziel, Chris. 'How to Adjust the Carburetor on a McCulloch Chain Saw Model 310' accessed August 25, 2019. http://homeguides.sfgate.com/adjust-carburetor-mcculloch-chain-saw-model-310-101690.html
Note: Depending on which text editor you're pasting into, you might have to add the italics to the site name.

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