Briggs & Stratton 405013x50A Parts Manual

To change the oil, first run the engine for a few minutes to warm it up. Then, turn off the engine and remove the oil drain plug to let the old oil drain out completely. Replace the drain plug, add new oil as specified in the manual, and check the oil level with the dipstick.
If your tractor won't start, check the battery connections for corrosion, ensure the fuel tank has fresh fuel, and inspect the spark plug for damage. If these are all in good condition, the problem may be with the ignition switch or starter solenoid.
First, disconnect the spark plug wire and use a spark plug wrench to unscrew the old plug. Check the gap on the new spark plug using a feeler gauge, then screw it into the engine by hand before tightening it with the wrench. Reconnect the spark plug wire.
To clean the air filter, remove it from the housing and gently tap it to remove loose dirt. If it's a foam filter, wash it in soapy water, rinse, and let it dry. For paper filters, replace if excessively dirty. Reinstall the filter securely.
Check if the mower deck is level by measuring from the ground to the deck on each side. Adjust the leveling if necessary. Inspect the blades for damage or dullness and replace or sharpen them. Ensure that the tire pressure is even on all wheels.
An overheating engine may be caused by low coolant levels, a clogged air intake, or a faulty thermostat. Check and refill the coolant, clear any debris blocking the air intake, and consider replacing the thermostat if the problem persists.
Before storing, clean the tractor thoroughly, change the oil, and add fuel stabilizer to the gas tank. Disconnect the battery and store it in a cool, dry place. Inflate tires to the recommended pressure and cover the tractor to protect it from dust and moisture.
To adjust the drive belt tension, locate the belt tensioner and adjust the tensioner pulley according to the specifications in the manual. Ensure that the belt has the correct tension, allowing about 1/2 inch of play. Tighten all fasteners securely.
Excessive vibration can be caused by unbalanced blades, loose parts, or worn bearings. Check and balance the blades, tighten any loose bolts or fittings, and inspect the bearings for wear, replacing them if necessary.
To change the cutting height, ensure the tractor is on a level surface and turned off. Locate the cutting height adjustment lever or knob, and set it to the desired position. Verify that both sides of the deck are at the same height before operating.