How do I Adjust the Idle Speed of a 14.5 HP Briggs & Stratton Model 287707 Motor?

Updated April 17, 2017

Properly setting the idle speed of the Briggs & Stratton 14.5-hp engine is essential to ensuring reliable engine operation. If the idle speed is too low, the engine could easily stall when running at slow speed. On the other hand, a high idle will cause undesired operation throughout the entire rpm range, possibly leading to engine damage at high speed. A simple twist of the idle adjustment screw is all that's required to alter the idle speed.

Start the engine. Place the throttle control (which is typically labelled with a turtle on one end and a hair on the other) in the "slow" position. Allow the engine to warm up for five minutes before continuing.

Clip the black cable of a hand-held tachometer to any unpainted metal area of the engine. Clip the red cable to the spark plug. It is not necessary to disconnect or remove the spark plug; the tachometer is sensitive enough to detect the electrical field fluctuation around the plug. An rpm reading will appear on the screen.

Rotate the throttle lever located on top of the carburettor until it hits the idle speed screw. Using a flathead screwdriver, adjust the idle speed screw until the tachometer reads 1750rpm. Rotate the idle mixture valve as far as it will go clockwise, then back counterclockwise, then leave it set it in the middle of its travel. Check the idle speed again and reset to 1750rpm if it has changed.

Push the throttle to the "fast" setting and listen to the engine. It should accelerate in a smooth fashion. If not, turn the idle mixture valve counterclockwise a 1/8 turn.


If a tachometer is not available, you can still adjust the idle speed, although the engine may not function as smoothly since the adjustment isn't as accurate. Simply set the idle screw to slightly faster than the point at which the engine begins to stall at idle.


Do not remove the limiter caps from the idle mixture valve or force it beyond its intended length of travel.

Things You'll Need

  • Hand-held tachometer
  • Flathead screwdriver
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About the Author

Ryan Bauer is a freelance writer located in Ozark, Missouri. He has written numerous articles and books, including "How to Improve Your Credit Score 100 Points in 100 Days." Bauer is an experienced automotive mechanic and computer technician.