Craftsman 917378491 gas walk-behind lawn mower Parts

For Craftsman gas walk-behind mower model 917378491, the serial number tells you the mower’s build information, but the most reliable way to tie it to an exact “age” is to match the serial number from the mower’s decal to the date-of-purchase you recorded and the model’s documentation. The serial number decal is on the rear of the mower housing. See the 917378491 owner's manual for the exact decal location and record fields.

Where to find the serial number on this mower

The model and serial numbers are printed on a decal on the rear of the lawn mower housing.

• Tip the mower only as recommended for service (avoid spilling fuel and oil)
• Wipe the rear housing clean so the decal is readable
• Write down the full serial number exactly as shown
• Record the date of purchase next to it for future reference

How to estimate the mower’s age from the serial number

Many outdoor power equipment serial numbers include a date code (often year and week, or year and month) near the beginning of the serial. If your serial includes a recognizable date code, you can estimate the manufacturing timeframe.

• Look for a 2-digit year (YY) followed by a week (WW) or month (MM)
• If there are multiple number groups, use the earliest group that looks like a date
• Compare the estimated build timeframe to your purchase date (purchase is usually after build)
• If the serial is purely sequential, use the purchase date as the practical “age” reference

Quick reference: common date-code patterns

What you see in the serial	Usually means	Example interpretation
YYWW	year + week of year	2315 = week 15 of 2023
YYMM	year + month	2304 = April 2023
MMDDYY	month/day/year	041523 = April 15, 2023

Why it matters

Knowing the approximate build date helps when you are choosing compatible parts (blade, drive belt, control cable) and planning maintenance intervals such as blade service, oil changes, and drive system checks.

Last updated: January 2026

The model number is 917.378491 (often written without the dot as 917378491) for this Craftsman gas walk-behind lawn mower. You can confirm the exact formatting and see the illustrated parts breakdown in the 917378491 owner's manual.

Where to find the model number on the mower

On most Craftsman walk-behind mowers, the model tag is on the deck or rear housing area. Check these common spots:

• Rear of the mower deck near the bagger door
• Top of the deck near the engine mounting area
• Side of the deck near a rear wheel
• On a label near the handle mounting brackets

Why you might see it written two ways

Both formats refer to the same mower; the dot is just a formatting style used in some manuals and parts lists.

Format you may see	What it means	Use it for
917.378491	Same model number with a dot	Manuals, diagrams, some labels
917378491	Same model number without a dot	Parts lookup, ordering, searches

Why it matters

Using the exact model number helps us match the correct Craftsman parts and diagrams for your mower, especially for drive system items like the lawn mower ground drive belt, 3/8 x 33-9/16-in 532169778 and control components.

Last updated: January 2026

For the Craftsman 917378491 gas walk-behind lawn mower, 87-octane regular unleaded gas is the right choice for normal operation. Higher octane (like 91) does not add power in small mower engines; the bigger priority is using fresh fuel and managing ethanol-related storage issues as outlined in the 917378491 owner's manual.

What to use (and what to avoid)

• Use 87 octane regular unleaded for everyday mowing.
• Use fresh gasoline; stale fuel is a common no-start cause.
• Avoid storing fuel in the mower for 30 days or longer; drain the tank and run the engine until the carburetor is empty for storage.
• Avoid fuel that has absorbed moisture; ethanol blends can attract moisture and cause fuel separation during storage.
• Do not add engine or carburetor cleaner products directly to the fuel tank.

Quick decision guide

Situation	Best choice	Why
Weekly mowing during the season	87 octane, fresh	Reliable starting and normal performance
Mower will sit 30+ days	Drain tank and run dry	Helps prevent fuel system damage from degraded fuel
Hard starting after storage	Replace with fresh fuel	Stale fuel and water in fuel are common culprits

Why it matters

Most mower performance and starting problems come from fuel freshness and storage, not octane rating. The manual specifically warns that alcohol-blended fuels can attract moisture and form acids during storage, which can damage the fuel system; using fresh fuel and proper storage steps protects the carburetor and fuel lines.

Related maintenance that helps starting

• Check engine oil level before each use.
• Keep the engine area clean; a clogged engine runs hotter and shortens engine life.
• If the mower will not start, check basics like fuel condition, air filter condition, and spark plug condition.

Last updated: January 2026