How much does it cost to replace a riding lawn mower engine?
For a Craftsman riding lawn tractor like model 917270621, a full engine replacement (parts plus labor) typically runs about $260 to $1,800, with around 6 labor hours common for a riding mower engine swap. Exact cost depends on the engine type, shop rates, and any extra parts needed.
- Engine price: new, rebuilt, or used engine options vary widely
- Labor rate: local shop rates and minimum charges
- Extra parts: belts, pulleys, wiring, fuel line, or mounting hardware found worn during teardown
- Tune-up and setup: throttle/choke adjustment, governor setup, and blade engagement checks
- Pickup/delivery: transport or trip charges if you are not bringing the tractor in
| Cost item | Typical range | Notes |
|---|---|---|
| Replacement engine | $200 to $1,500 | Biggest variable; depends on horsepower and crankshaft specs |
| Labor | $200 to $600 | Often based on ~6 hours for riding mowers |
| Misc. parts/fluids | $20 to $200 | Oil, filter, fuel filter, clamps, hardware |
If the tractor will not start or cranks poorly, we recommend ruling out common no-start causes first. These checks often cost far less than an engine swap:
- Verify the battery is strong and cable connections are clean and tight
- Confirm the operator presence and interlock system is working (the manual calls for checking it regularly)
- Check engine oil level and basic maintenance items (air filter, spark plug)
- If it clicks but will not crank, test the starter circuit and solenoid
For model-specific maintenance intervals and troubleshooting steps, use the 917270621 owner's manual.
Engine replacement is one of the highest-cost repairs on a riding mower. A quick diagnostic and maintenance check can prevent unnecessary replacement and can also protect the new engine if you do install one.
Last updated: January 2026
What engine is in a Craftsman 917270621?
The Craftsman tractor model 917270621 is shown in our documentation with a Briggs & Stratton engine model 28U707, type 1174-E1. For the most accurate match to your exact tractor, confirm the model and type on the engine ID label and compare it to the 917270621 owner's manual.
Use the engine’s ID label as the final check, especially if the tractor was repowered.
- Park on a level surface, set the parking brake, and remove the key
- Find the Briggs & Stratton ID label (commonly on the blower housing, valve cover area, or near the starter)
- Record the model, type, and code from the label
- Match 28U707 and 1174-E1 to the engine listing in the manual
- Use the full model and type when selecting carburetor, ignition, and gasket parts
| Engine ID item | Example for this tractor | What it’s used for |
|---|---|---|
| Model | 28U707 | Identifies the engine family and core configuration |
| Type | 1174-E1 | Identifies the exact build variation for correct parts |
| Code | Varies by engine | Indicates the production date for running changes |
Briggs & Stratton engines can look similar across multiple Craftsman tractors. Using the correct model and type prevents wrong-part returns and speeds up troubleshooting for issues like hard starting, stalling, or poor fuel delivery.
Last updated: January 2026
Who makes the Craftsman 420cc engine?
On the Craftsman lawn tractor model 917.270621, the owner’s manual identifies the engine as a Briggs & Stratton 15.5 HP engine (often shown as “B&S” in parts listings). That means this tractor is not a Craftsman 420cc-engine model.
Use these quick checks to match the engine to your tractor:
- Look for the engine brand badge on the blower housing (top of the engine)
- Check the engine model and type numbers stamped on the engine shroud
- Compare the engine information to the specifications section in the 917.270621 owner’s manual
- Verify the tractor model number on the frame tag matches 917.270621
- If the engine was replaced, use the replacement engine’s model/type numbers (not the tractor model)
“420cc” is a displacement rating used on some single-cylinder engines. Craftsman-branded equipment can be built with engines sourced from different manufacturers depending on the product line and year.
| What you’re looking at | What to use for identification | What it tells you |
|---|---|---|
| Tractor model tag | Tractor model number (917.270621) | Which tractor parts fit |
| Engine shroud stamping | Engine model/type/code | Who made the engine and which engine parts fit |
| Owner’s manual specs | HP, tune-up specs, capacities | Maintenance requirements |
Engine manufacturer and engine model numbers determine the correct tune-up parts (spark plug, air filter, fuel filter) and service procedures. Using “420cc” alone can lead to ordering the wrong parts.
Last updated: January 2026





