Lawn-Boy 17739 - User Manual

This document is an operator's manual for a Lawn-Boy 21-inch mulching/rear bagging lawn mower, specifically models 10739 and 17739 (serial numbers 316000001 and up). It provides comprehensive instructions for safe operation, maintenance, and storage of the device.

Function Description

The Lawn-Boy 21-inch mulching/rear bagging lawn mower is a rotary-blade, walk-behind machine designed for residential homeowners. Its primary function is to cut grass on well-maintained lawns. The mower offers two main modes of operation: mulching and rear bagging. In mulching mode, the mower finely cuts grass and leaf clippings and redistributes them back onto the lawn, acting as a natural fertilizer. In rear bagging mode, the mower collects clippings into an attached grass bag, which is useful for maintaining a tidy lawn or when dealing with excessive clippings. The mower is powered by an internal combustion engine, and its self-propel drive system assists the operator in moving the machine across the lawn.

Usage Features

The manual emphasizes safety as a paramount aspect of using the mower. Before operation, users are instructed to read the entire manual, ensure all guards and safety devices are in place, and inspect the machine for any worn or damaged parts, especially the blades. The cutting height is adjustable, with settings ranging from 32 mm (1-1/4 inches) to 95 mm (3-3/4 inches), allowing users to customize the lawn's appearance. Adjusting the cutting height requires stopping the engine and waiting for all moving parts to cease.

Fueling the mower requires unleaded gasoline with an octane rating of 87 or higher, and the manual specifically warns against using gasoline with more than 10% ethanol (E15, E20, E85 are not approved). Fuel stabilizer is recommended for year-round use to prevent starting problems. The engine oil level must be checked before each use, and the crankcase capacity is 0.53 L (18 oz) of 10W-30 or SAE 30 detergent oil.

Starting the engine involves holding the blade-control bar against the handle and pulling the recoil-start handle. For models with electric start, an ignition key is also used. The self-propel drive is engaged by squeezing the self-propel drive bar towards the handle. The self-propel speed is fixed, but the operator can reduce ground speed by increasing the space between the self-propel drive bar and the handle. To shut off the engine, the blade-control bar is released, which should stop both the engine and blade within 3 seconds.

When mowing, the manual advises cutting only about a third of the grass blade at a time and recommends mowing in dry conditions to avoid slipping and contact with the blade. For tall grass (over 15 cm or 6 inches), it suggests mowing at the highest setting first, then at a lower setting for a better finish. Alternating mowing direction helps disperse clippings evenly. For cutting leaves, the manual recommends ensuring half of the lawn shows through the cut leaf cover and slowing down if the leaves are not finely cut.

The handle can be folded for storage or transport by loosening the handle knobs and moving the handle forward. This feature helps in reducing the mower's footprint.

Maintenance Features

The manual provides a detailed recommended maintenance schedule to ensure the mower's longevity and safe operation.

Before each use or daily: Check engine oil level and ensure the engine shuts off within 3 seconds of releasing the blade-control bar.
After each use: Clean grass clippings and dirt from under the machine.
Every 25 hours: Check the air cleaner for dirty, loose, or damaged parts, and clean or replace as needed.
Every 100 hours: Replace the air cleaner element (more frequently in dusty conditions), clean the cooling system (refer to engine owner's manual), and replace the spark plug.
Before storage: Empty the fuel tank and perform annual storage procedures.
Yearly: Replace or sharpen the blade (more frequently if dull) and refer to the engine owner's manual for additional yearly maintenance.

Before any maintenance, the engine must be shut off, all moving parts stopped, and the spark-plug wire disconnected to prevent accidental starting. The blade is sharp, so gloves and eye protection are required when servicing it. Tipping the machine for oil changes or blade replacement should only be done after the fuel tank runs dry, or by using a hand fuel pump to remove fuel. The machine should always be tipped with the dipstick down.

Servicing the air cleaner involves pressing down on latch tabs, opening the cover, replacing the element, and reinstalling the cover. Changing the engine oil, while not strictly required, can be done by warming the engine, tipping the machine with the dipstick down to drain the old oil, and then refilling with new oil.

Blade replacement requires a torque wrench to tighten the blade bolt to 82 N-m (60 ft-lb). The manual stresses the importance of proper tightening and warns against overtightening. The self-propel drive cable tension can be adjusted by turning a knob; pushing the cable toward the engine increases traction, while pulling it away decreases traction.

For storage, the mower should be kept in a cool, clean, dry place. The manual outlines a specific procedure for preparing the machine for storage, including adding fuel stabilizer, running the engine dry, and adding oil to the cylinder through the spark plug hole to prevent corrosion. When removing the machine from storage, the spark plug is reinstalled, fasteners are checked, the engine oil level is verified, and the fuel tank is refilled with fresh gasoline.