My 6.5Hp B&S Lawn Mower Will Not Start After Cleaning the Underside

Crankshaft

• If you used the wrong cleaning solutions on your 6.5 Horsepower Briggs and Stratton mower, you may have compromised the crankshaft in the underside of your mower. Your mower blade is attached to the crankshaft, which spins as the engine’s pistons push down during the combustion cycle. If the crankshaft is seized from rusting or interference, the pistons can’t move, thus inhibiting a start. Ensure you use only approved cleaners on the underside of your mower. Keep water off the crankshaft and lubricate it with engine oil according to the maintenance schedule.

Gas

• If you didn’t empty your gas tank before you cleaned the underside, it’s possible that you emptied it accidentally. Although your mower has a gas cap, that doesn’t guarantee gas won’t escape from it. An empty tank won’t provide enough gas for ignition. Even if you didn’t spill all the gas, there still must be enough to pump through the primer into the carburetor for ignition.

Oil

• Oil can also leak from your Briggs and Stratton engine if you tilt it the wrong way while cleaning the underside. Oil can spill from the crankcase into the combustion chamber and out of the exhaust pipe. While having no oil won’t prevent a start, your engine won’t run long without lubrication for its hot, moving parts. The pistons will seize from the heat and fuse to the cylinder, preventing the necessary compression for combustion. If oil leaks into the carburetor, it interferes with the fuel-air mixture required for ignition.

Drain Port

• A drain port plug is located in your mower’s underside for the oil crankcase. To change your engine oil, you must open this drain port with a 3/8 drive ratchet and extension. If this drain port isn’t closed all the way, all of your oil can leak out of it over time and cause engine seizures. Check its condition while cleaning the underside. Replace the drain port plug if it looks rusted or broken.