Craftsman 917387270 rotary lawn mower Parts

Common problems on the Craftsman 917387270 rotary lawn mower are no-start conditions (often fuel, air, or ignition related), loss of power in heavy grass, uneven cutting, excessive vibration, and a starter rope that’s hard to pull. Our owner's manual troubleshooting chart covers these symptoms and the most likely causes.

Quick checks we recommend first

• Use fresh gasoline; old fuel causes hard starting and surging.
• Check the air filter; a dirty filter commonly causes loss of power.
• Inspect the spark plug and make sure the wire is firmly connected.
• Look under the deck for grass and debris buildup (with the spark plug wire disconnected).
• Verify the control bar is fully depressed to the handle when starting.
• Confirm the oil level is correct; too much oil can cause running issues.

Symptom-to-cause guide (most common)

Symptom	Most likely causes	What to do next
Won’t start	Dirty air filter, empty/old fuel, spark plug issue, control bar not engaged, flooded engine from over-priming	Refresh fuel, service air filter and plug, follow correct priming steps
Loss of power	Cutting too much grass, dirty air filter, deck packed with clippings, walking speed too fast	Raise cut height, clean deck, slow down, clean/replace filter
Uneven cut	Wheel heights uneven, blade worn/bent, deck buildup	Set wheels to same height, clean deck, inspect blade
Excessive vibration	Worn/bent/loose blade, bent crankshaft, debris under deck	Stop mowing; inspect blade and mounting hardware
Starter rope hard to pull	Blade dragging in grass, brake engaged when control bar released, blade adapter issue, possible bent crankshaft	Clear deck, check blade area and adapter before restarting

Parts that commonly get involved

If you find looseness at the blade mounting point or damage after a vibration event, the blade mounting hardware and adapter area are the first places to inspect.

• Lawn mower blade adapter 581547901 (connects the blade to the engine shaft)
• Lock nut 532409149 (common fastener used on mower assemblies)
• Washer 532851074 (helps clamp and space hardware correctly)

Why it matters

Running with a loose, bent, or obstructed blade can cause severe vibration, poor cut quality, and harder starting. Cleaning the deck and keeping the blade system tight protects the engine and improves bagging and discharge performance.

Last updated: February 2026

For the Craftsman 917387270 push mower, we recommend unleaded regular gasoline; the owner’s manual lists a 1.5-quart fuel capacity and specifies unleaded regular as the correct fuel type. For exact operating and maintenance details, follow the owner's manual.

What to use (and what to avoid)

Use fresh fuel that matches what small 4-cycle mower engines are designed for.

• Use unleaded regular gasoline
• Use fresh gas (older fuel causes hard starting and rough running)
• Avoid E85 (high-ethanol fuel) in small engines
• Avoid E15 unless your fuel cap/manual specifically approves it
• Do not mix oil into the gas (this is a 4-cycle mower)

Quick fuel guidance for small engines

Fuel type at the pump	Typical label	Use in Craftsman 917387270?
Regular unleaded	E0 to E10	Yes
Unleaded with higher ethanol	E15	No
Flex-fuel	E85	No

Why it matters

Using the right gasoline helps prevent carburetor varnish, fuel-system corrosion, and starting problems. Higher-ethanol fuels can attract moisture and run leaner in small engines, which leads to poor performance and expensive repairs.

Helpful related maintenance tips

• If the mower sits more than a few weeks, add fuel stabilizer and run the engine briefly
• Store fuel in an approved container and keep it tightly sealed
• If you suspect bad gas, drain the tank and refill with fresh unleaded regular
• Keep the blade sharp to reduce engine load; see how to sharpen a lawn mower blade

Last updated: February 2026

On your Craftsman 917387270 walk-behind mower, the blade is held on with a blade bolt (not a blade nut); it threads into the blade adapter/crankshaft and tightens clockwise. For the exact fastener callout and blade service steps, use the owner's manual.

What fastener this model uses (and why your question comes up)

“Blade nut size” is common on riding mowers, but this rotary walk-behind mower uses a bolt-and-washer stack instead.

Typical blade bolt stack on this style of mower:

• Blade bolt (Grade 8)
• Lockwasher
• Hardened washer
• Blade
• Blade adapter

How to remove the blade bolt safely

• Disconnect the spark plug wire and keep it away from the plug.
• Tip the mower with the air filter/carburetor side up (to reduce fuel/oil leakage).
• Wedge a block of wood between the blade and the mower housing to stop rotation.
• Turn the blade bolt counterclockwise to loosen.
• Inspect the blade adapter for cracks or wallowed-out keyway; replace if damaged.

Tightening spec for Craftsman 917387270

The manual’s recommended tightening torque for the blade bolt is:

Item	Spec for model 917387270
Blade bolt torque	35 to 40 ft-lbs
Bolt grade	Grade 8 (heat treated)

Parts that commonly get replaced during blade service

If the blade feels loose, wobbles, or won’t stay tight, the adapter or hardware is often the cause.

• Lawn mower blade adapter 581547901 (common wear item if the blade hits rocks/roots)
• Lock nut 532409149 (used in other assemblies on this mower; replace if threads are damaged)

Why it matters

Using the correct blade fastener type and torque helps prevent blade vibration, protects the crankshaft, and reduces the chance of stripping the blade adapter. It also helps the mower cut evenly and reduces deck noise.

Last updated: February 2026