Craftsman 917378850 rotary lawn mower Parts

For a Craftsman rotary lawn mower like model 917378850, the serial number is typically used to identify the production date and factory; the exact format can vary by engine and manufacturing run. We recommend matching the serial number format shown in the 917378850 owner's manual and then decoding it by the date-code pattern used on your specific label.

Where to find the serial number

Most walk-behind mowers have the serial number on a sticker or stamped plate. Check these common spots:

• On the rear of the mower deck near the discharge opening
• On the top of the deck near the engine mounting area
• On the handle bracket area (near the lower handle bolts)
• Near the wheel height adjuster area
• On the engine shroud (engine serial is separate from mower serial)

How to decode it (what to look for)

Craftsman serial numbers are not all identical, so start by identifying the pattern on your label.

• Look for a clearly separated date code (often 6 digits)
• Check whether the label calls out DOM (date of manufacture) or similar wording
• If you see 6 digits, it is commonly read as MMDDYY (month, day, year)
• If you see 8 digits, it is commonly read as MMDDYYYY
• If the label includes letters, those often indicate plant or line information

Common date-code examples

Example code	Common readout	Meaning
072811	MMDDYY	July 28, 2011
031520	MMDDYY	March 15, 2020
07042021	MMDDYYYY	July 4, 2021

Why it matters

Reading the serial number correctly helps us match the right parts and diagrams for your mower, especially for wear items like the drive system, handle hardware, and wheel adjusters.

Parts that often depend on the exact build

• Drive components (belt, gearcase, pinion)
• Control cables and handle assemblies
• Wheel and height adjuster hardware

If you are troubleshooting drive issues, the lawn mower wont move troubleshooting video motion drive failure guide pairs well with confirming your exact serial/date code.

Last updated: January 2026

For the Craftsman rotary lawn mower model 917378850, regular 87-octane unleaded gas is the right choice for normal mowing. Higher octane (like 91) does not add power or make the engine run better in this type of mower; using clean, fresh fuel matters more. For model-specific fuel and operation notes, use the 917378850 owner's manual.

What to use (and what to avoid)

• Use fresh, regular unleaded 87-octane gasoline.
• Avoid using “premium” (91) as a routine habit; it typically provides no benefit in small mower engines.
• Do not use stale fuel (old gas is a common no-start cause).
• Keep fuel clean; dirt or water in fuel can create starting and running problems.
• If the mower will sit, use a fuel stabilizer and follow the storage steps in the manual.

Quick comparison

Fuel choice	OK for 917378850?	What you’ll notice
87 octane (regular)	Yes	Normal starting and performance
91 octane (premium)	Yes, but unnecessary	Usually no improvement
Old/stale gas	No	Hard starting, rough running, no-start
Gas contaminated with water/dirt	No	Surging, stalling, no-start

Why it matters

Octane mainly relates to resistance to knock in higher-compression engines. Most walk-behind mower engines are designed to run correctly on regular fuel, so fuel freshness and cleanliness have a bigger impact than octane on starting, power, and engine life.

If your mower won’t start after fueling

We use this fast checklist because the manual’s troubleshooting points often come down to fuel quality and basic ignition:

• Confirm the tank has fresh gas (not last season’s).
• Check for signs of water in fuel (milky look, sputtering).
• Inspect the air filter for heavy dirt.
• Verify the spark plug wire is firmly connected.
• If the rope is hard to pull or stuck, follow lawn mower pull cord stuck.

Last updated: January 2026

The model number for this Craftsman walk-behind mower is 917.378850 (often written without the dot as 917378850). You’ll see it printed on the mower’s model tag and on the cover page of the 917378850 owner's manual.

Where to find the model number on the mower

We recommend checking these common locations on Craftsman rotary lawn mowers:

• On the rear of the mower deck near the discharge door
• On the side of the deck near a rear wheel
• Near the handle mounting brackets
• On a label close to the engine mounting area

Why the dot matters (917.378850 vs 917378850)

Both formats refer to the same mower; the dot is a formatting style used in many manuals.

You might see it as	What it means	When it’s used
917.378850	Same model number	Common in printed manuals and diagrams
917378850	Same model number	Common on parts sites and model lookups

Tips to avoid ordering the wrong parts

When you’re matching parts (like a wheel, belt, or control cable), we use the full model number to ensure the correct fit.

• Match the model number exactly: 917378850
• Use the parts diagram in the 917378850 owner's manual to confirm the part location
• If your label is worn, compare the mower’s major assemblies (handle, drive system, deck) to the diagram

Example parts that are model-specific

These are common items that vary by model and are worth double-checking before ordering:

• Upper handle 583703501
• Lawn mower engine zone control cable 532184588
• Lawn mower ground drive belt, 3/8 x 32-1/2-in 532175436

Why it matters

Using the exact model number helps us match the correct Craftsman parts list and diagrams, which prevents fit issues and reduces downtime when you’re repairing or maintaining the mower.

Last updated: January 2026