How to Adjust the Idle on a Toro Mower

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Tip

Your owner's manual can provide additional diagrams to assist in locating and correctly removing and replacing the air filter.

Warning

You'll have to run the engine to decide if the idle speed is correct. Stay clear of moving parts, especially mower blades, while working on or around running machinery.

When a lawn mower engine runs roughly, irregularly, too fast or too slow, you can adjust the idle speed with just a few turns of some screws. Because Toro uses a 4-cycle Briggs & Stratton engine in most of its outdoor power equipment -- from walk-behind mowers, to riding mowers, to snowblowers and small tractors -- adjustment is fairly universal and works from one model to another.

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Step 1

Position the mower on a flat, even surface. Start the engine and let it run for about five minutes to reach normal operating temperature. Then turn the mower off and remove the air filter with a screwdriver.

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Step 2

Locate the three carburetor adjustment screws on the mower's carburetor. The idler-speed screw will be near the top, the idle-mixture screw in the center and the idler-power screw on the bottom.

Step 3

Turn the idler-power screw clockwise with a screwdriver until it becomes tight and no longer turns. Once turned all the way clockwise, back it off one full turn or 360 degrees with a screwdriver.

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Step 4

Turn the idle-mixture screw clockwise also with a screwdriver until it does not turn any more or meets heavy resistance. Turn the idle-mixture screw clockwise 1-1/2 turns or 540 degrees.

Step 5

Start the Toro lawn mower and let it idle for one to two minutes. Rotate the throttle control to the highest speed. Turn the idler-power screw 1/8 to 1/4 turn clockwise with a screwdriver until the engine begins to sputter, counting the number of turns. Then turn the idler-power screw counterclockwise 1/8 to 1/4 turn until it begins to stall, counting the turns. Set the idler-power screw in between those two positions. The engine should run smoothly in this position.

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Step 6

Rotate the Toro's throttle control back to normal. Turn the engine's idler-speed screw clockwise with a screwdriver until it reaches its highest idling speed.

Step 7

Repeat the same process with the idler-mixture screw, turning it 1/8 to 1/4 turn clockwise until the mower's engine begins to sputter, counting the number of turns. Then turn the idler-mixture screw counterclockwise 1/8 to 1/4 turn until it begins to stall, counting the turns. Set the idler-mixture screw at the midpoint of each position.

Step 8

Turn the Toro's idler-speed screw counterclockwise with a screwdriver until it idles normally.

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references

Owen E. Richason IV

Owen Richason grew up working in his family's small contracting business. He later became an outplacement consultant, then a retail business consultant. Richason is a former personal finance and business writer for "Tampa Bay Business and Financier." He now writes for various publications, websites and blogs.