Where is the drain plug on a Briggs & Stratton lawn mower? Dennis Walden Sep 12, 2021. Typically, however, on vertical shaft engines, the oil drain plug is located beneath the engine block near the crankshaft. To remove the square plug, all that is required is a standard size 3/8" ratchet and extension (no socket). Place your riding mower on flat level surface. Turn the mower off. Make sure the engine is cool. Remove the ignition key. Disconnect the spark plug ignition wire. Clean the oil fill and drain area of any debris. Remove the dipstick from oil fill tube. If using the Arnold siphon pump, place the black tube into the dipstick hole on the engine KnH9i6. 350 102 233 246 209 47 235 243 9

briggs and stratton oil drain plug location