Craftsman 917370721 lawn mower Parts

For Craftsman walk-behind mower model 917370721, the serial number tells you the mower’s build sequence, but the most reliable way to determine age is to match the serial number on the rear housing decal to the date information and identification guidance in the 917370721 owner's manual.

Where to find the serial number on this model

On model 917370721, we look for the model and serial number decal on the rear of the lawn mower housing.

• Tip the handle forward and look at the rear deck area
• Wipe off grass and dirt so every character is readable
• Write down the full serial number exactly as shown
• Record the date of purchase too (it helps confirm the timeframe)

How serial numbers usually indicate age

Many mower serial numbers include a date code, but formats vary by engine and mower manufacturer. Use these common patterns as a quick check, then confirm using the manual and parts diagrams.

• YYMMDD: year, month, day
• MMDDYY: month, day, year
• YYWW: year and production week
• YYMM: year and month

Quick decode table (examples)

If the serial starts with	It often means	Example result
YYMMDD	Built on a specific date	230615 = June 15, 2023
YYWW	Built in a production week	2412 = week 12 of 2024
MMDDYY	Built on a specific date	061523 = June 15, 2023

Why it matters

Knowing the mower’s age helps us choose the right maintenance parts and specs for your Craftsman 917370721, such as the correct blade hardware torque and tune-up items listed in the manual.

Helpful next steps if the serial format is unclear

• Compare the serial decal to the identification section in the 917370721 owner's manual
• Check the engine label separately (engine serial formats can differ from the mower’s)
• Use your purchase date as a practical “in-service” age reference

Last updated: January 2026

For the Craftsman lawn mower model 917370721, we recommend using fresh 87-octane (regular) unleaded gasoline for normal mowing. Higher octane (like 91) does not add power in small mower engines; fuel freshness and proper storage matter far more for easy starting and smooth running.

What to use (and what to avoid)

• Use 87 octane regular unleaded from a clean, approved gas can.
• Avoid stale fuel; old gas is a common cause of hard starting and rough running.
• Keep dirt and rust out of your fuel supply; a rusty can can contaminate gas.
• Do not store gasoline from one season to the next.
• Follow the fuel and storage guidance in the 917370721 owner's manual.

Quick comparison: 87 vs 91 for a walk-behind mower

Fuel choice	Best use case	What you’ll notice
87 octane (regular)	Everyday mowing	Normal performance and reliable operation
91 octane (premium)	Not needed for most mower engines	Typically no performance benefit

If your mower is hard to start after sitting

Stale fuel is specifically called out in the troubleshooting guidance for this mower. If it ran fine last season but struggles now, start with fuel quality and basic tune-up checks.

• Drain/replace old fuel with fresh 87 octane
• Check the air filter and spark plug condition
• Make sure the spark plug wire is firmly connected
• Inspect for a loose blade or a worn blade adapter (these can cause vibration and poor cutting)

Why it matters

Using the right fuel is less about octane and more about preventing varnish, moisture issues, and contamination that lead to no-start problems. The manual also emphasizes safe handling and storage practices to reduce fuel-related issues.

Last updated: January 2026

The model number is 917.370721 (often written without the dot as 917370721) for this Craftsman walk-behind gas lawn mower. You’ll see it printed on the mower’s model label and on the cover page of the 917370721 owner's manual.

Where to find the model number on the mower

We recommend checking these common locations first:

• On the rear of the mower deck near the discharge opening
• On the handle support area (near the lower handle brackets)
• Near the engine mounting area on the deck
• On a sticker or metal tag that also lists serial information

Why the dot matters (917.370721 vs 917370721)

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

You might see it as	What it means	When it’s used
917.370721	Same model number	Owner’s manual, diagrams
917370721	Same model number	Online parts lookup, ordering

Why it matters when ordering parts

Using the exact model number helps us match the correct diagrams and parts for your mower’s drive system, handle hardware, and cutting deck components.

• Confirms the correct parts list for your mower
• Helps avoid ordering look-alike parts that do not fit
• Speeds up troubleshooting and maintenance steps

Quick example (parts that vary by model)

If you’re servicing the self-propel system, the correct drive control and cable routing depend on the model. For this mower, the parts list includes items like the lawn mower drive control 583230601.

Last updated: January 2026