How to Time a Briggs Engine

Lawn mowers often have Briggs and Stratton engines.

Briggs engines run motor devices with low horsepower, such as lawn mowers. These motors can occasionally malfunction, and require proper timing to work as they should. Briggs engines work by using internal combustion: the spark from your spark plug ignites the fuel-air mix inside the valve, where it expands and presses the piston and crankshaft. Timing an engine refers to the act of realigning the flywheel, valve, piston and spark plug so the spark ignites the fuel inside the valve.

Things You'll Need

• Owner's manual
• Wrench
• Flywheel puller
• New flywheel key
• Flathead screwdriver
• Wood block

Instructions

1. Disconnect the spark plug lead to prevent the engine from accidentally starting during maintenance. Secure the blade with a wood block.

2. Access the flywheel. On a lawnmower, where Briggs engines are most commonly used, you can access the flywheel by removing the cowl, or blower cover. According to RepairFAQ, the timing of a Briggs engine can fail when the engine stops suddenly. The resulting damage to the flywheel key may loosen the flywheel.

3. Place the flywheel puller onto the flywheel. Tighten the nuts evenly until the flywheel comes free of the crankshaft. Remove it, along with the flywheel key.

4. Inspect the flywheel key. According to Briggs and Stratton, the flywheel key consists of soft metal that can absorb the shock of impact to prevent damage to other parts of the engine. The flywheel key holds the flywheel to the crankshaft and keeps the engine perfectly timed. Often, you will find that the key has been bent or sheared.

5. Use a flathead screwdriver to pry the old key loose. Discard it. Clean the keyway slots of any debris. Slide the flywheel back onto the crankshaft, aligning the two keyway slots perfectly before inserting the new flywheel key. Tap it gently to secure it in place, then reattach the flywheel nuts.

6. Reattach the blower cover and reconnect the spark plug lead.

References

• RepairFAQ.org: Lawnmower Timing
• BriggsAndStratton.com: Inspecting the Flywheel and Key