The Toro 51978 is a commercial-grade walk-behind mower designed for professional landscaping and heavy-duty residential use. This parts manual provides detailed information on all components, assemblies, and replacement parts for the Toro 51978 mower, including the engine, cutting deck, drive system, controls, and safety features. Below are key sections for identification, engine parts, deck assembly, drive train, controls, maintenance parts, and ordering information.
Key identifiers: Model number 51978, Serial number location on frame near engine mount. Engine: Toro Commercial 190cc OHV engine. Cutting Width: 21 inches. Drive Type: Self-propelled rear-wheel drive. Fuel Type: Unleaded gasoline. Oil Capacity: 20 oz. Deck Material: 11-gauge steel.
| Specification | Description |
|---|---|
| Model Number | 51978 |
| Engine Type | Toro Commercial 190cc OHV, 4-cycle |
| Cutting Width | 21 inches |
| Drive System | Self-propelled, variable speed |
| Fuel Tank Capacity | 1.1 quarts |
| Deck Height Adjustments | 7 positions (1-3.5 inches) |
| Starter Type | Recoil |
| Wheel Size (Front/Rear) | 8 inches / 11 inches |
| Weight | 85 lbs |
| Warranty | Commercial 3-year limited |
Complete breakdown of the Toro 190cc OHV engine and related parts.
WARNING! Disconnect spark plug before servicing engine components. Use only Toro-approved replacement parts.
Parts for the 21-inch cutting deck, blade system, and height adjustment.
CAUTION! Always ensure blades are stopped and engine is off before accessing deck components.
Handle assembly, control levers, and operator interface components.
Handle: Main handlebar with grip, part number 51978-005. Control Levers: Drive control lever, blade engagement lever. Cables: Throttle cable, drive control cable, blade engagement cable. Bail Arm: Operator presence control (safety bail). Height Adjust Lever: Lever for cutting height adjustment. Hardware: Bolts, nuts, and brackets for assembly.
Front and rear wheel assemblies, axles, and bearing components.
Tip: Lubricate axle points periodically to ensure smooth operation.
Safety switches, interlocks, and protective components.
WARNING! Never bypass safety interlocks. Replace faulty safety components immediately.
Recommended maintenance parts and kit assemblies.
Air Filter Kit: Includes pre-filter and main filter. Spark Plug: Toro approved replacement. Oil Change Kit: Oil and filter. Blade Sharpening Kit: Blade balancer and sharpening stone. Belt Replacement Kit: Deck and drive belts. Tune-Up Kit: Includes air filter, spark plug, oil.
Bolts, nuts, washers, and specialized fasteners for assembly.
CAUTION! Use only grade-5 or higher hardware for structural components. Refer to torque specifications.
Detailed exploded-view diagrams for each assembly with part numbers and quantities.
Diagram 1: Engine Assembly (Page 12). Diagram 2: Cutting Deck (Page 14). Diagram 3: Drive System (Page 16). Diagram 4: Control Assembly (Page 18). Diagram 5: Wheel & Axle (Page 20). All diagrams include reference numbers corresponding to parts list.
| Issue | Possible Cause | Parts Solution |
|---|---|---|
| Engine won't start | Fuel system, spark plug | Replace fuel filter, spark plug (part 51978-010). |
| Poor cutting performance | Dull blade, deck wear | Replace blade (51978-002), check deck belt. |
| Drive system failure | Belt wear, transmission | Replace drive belt (51978-004). |
| Excessive vibration | Unbalanced blade, bearing | Replace blade or spindle bearing (51978-008). |
| Safety interlock failure | Faulty switch | Replace operator presence switch (51978-009). |
Ordering: Contact Toro Commercial Parts at 1-800-348-2424 or visit www.toro.com/en/parts.
Support: Technical assistance available at 1-888-384-9939.