NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Carburetor adjustments                  
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Carburetor adjustments

If your engine is relatively new (made within the last 10 years or so) and has only one speed, then there may be no adjustments (like the one discussed in the section: Cleaning Craftsman (Tecumseh) carburetors. It will either work or it won't - in which case it needs cleaning or parts replaced. Or your overhaul was less than 100% effective. You can tell if your carburetor is of this type as there will be no adjusting screws on the carburetor. For Craftsman types, there will be a solid hex nut on the bottom holding the float bowl in place. There may or may not be a primer button.

For adjustable types, it is best to refer to your engine manual. However, here is the general procedure. Some of the specific numbers may differ for your engine, however.

In all cases, before touching any adjustments, make sure your air filter is in place, and clean (or new). Fill the fuel tank about half full with fresh gasoline.

There are three adjustments on a typical carburetor:

Initially, carefully and gently turn the two mixture controls in until they just seat.

Note: "In" means clockwise (the way you would tighten a normal screw) and "out" means counterclockwise (the way you would loosen a normal screw).

CAUTION: do not force them - you are not trying to tighten anything - as you will damage the needles and seats which will require replacement of the needles or entire carburetor. Then back them out 1 to 1-1/2 turns. Set the idle speed screw 1 to 2 turns beyond where it contacts the throttle plate. Refer to your engine manual for specific recommendations! These settings should allow the engine to start and run, though perhaps not entirely smoothly or with great enthusiasm.

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