How to Replace a Spark Plug on a Cub Cadet Riding Mower

Learn where to find the Cub Cadet spark plug location, how to choose the correct replacement, and how to replace a riding lawn mower spark plug safely step by step.

Replacing a spark plug on a Cub Cadet riding mower is a maintenance job most owners can handle. Before buying a replacement, you need to figure out two main things: where is the spark plug on a riding lawn mower, and which engine is installed in your machine.

Cub Cadet uses several engine brands, including Kohler, Kawasaki, and Briggs & Stratton. That means searching only for a spark plug for cub cadet riding mower is not specific enough. Two mowers can look very similar but require different spark plugs, gap settings, or part numbers.

To keep things simple, we’ll use a Cub Cadet XT1 LT46 configuration equipped with a Kohler 7000 Series KT730 engine as our main example. Different XT1 LT46 versions may use different engines, so always confirm the engine model on your own machine before ordering parts.

Where Is the Spark Plug Located on a Cub Cadet Riding Mower?

On most machines, finding the riding mower spark plug location isn't hard. It's typically right on the side of the engine block under the hood.

• If you have a single-cylinder engine, you'll usually find one spark plug

• If it’s a V-twin engine, such as the Kohler 7000 Series, there are two spark plugs, with one on each cylinder.

How to Find Them:

1. Open the hood.

2. Find the thick wire that runs to the cylinder head.

3.  At the end of the wire, you’ll see a rubber cap.

4. The spark plug is right under it.

On the Kohler KT730, there is one spark plug on each cylinder head, on opposite sides of the engine.

UDC Parts expert tip: Always let the engine and exhaust cool down completely before grabbing that rubber boot. Working on a hot machine is a fast track to burned fingers and makes wrangling stiff wires a lot harder.

How to Select the Right Spark Plug for Your Cub Cadet

A common mistake is searching for a riding lawn mower spark plug by using a general name. This can easily lead to buying the wrong part.

Before you buy, make sure you know:

• The exact mower model

• The specific engine model

• The correct spark plug part number

• The required gap

• The correct torque specification

Cub Cadet maintenance kits for Kohler 7000 Series KT715–KT745 twin-cylinder engines include two Kohler 25 132 23-S / KH-25-132-23-S spark plugs. However, always confirm the correct part number for your specific engine before buying.

Keep this order in mind:

Mower model → Engine model → Spark plug part number → Gap → Torque

When Should You Change a Spark Plug?

If your machine starts having problems, check the spark plug. A complete removal makes it easier to inspect the plug for wear, fouling, or damage.

Some common warning signs include:

• The engine is hard to start.

• You notice ignition misfires while mowing.

• The engine has a rough idle or loses power under load.

• You notice a drop in cutting power.

• The electrode tips look worn or rounded.

• The ceramic insulator has a small crack.

• The tip is covered in heavy grime.

• You have reached the recommended maintenance interval.

Don’t rely on a simple “replace it once a year” rule. The correct service interval depends on your specific engine. For the KT730 and related Kohler 7000 Series engines covered by Kohler’s service manual, spark plug replacement and gap adjustment are listed at 500 operating hours. Always check the maintenance schedule for your exact engine and mower.

What You Need for the Job

For a smooth cub cadet spark plug replacement on a Kohler engine, you’ll need these tools:

• New spark plugs

• A 5/8" spark plug socket

• A standard ratchet

• An extension bar

• A wire feeler gauge or a dedicated spark plug gap tool

• A torque wrench

• A clean rag or brush

Note: If you are working on a V-twin engine, make sure you have two matching spark plugs.

Step-by-Step Guide: How to Change Spark Plugs

Step 1. Prep the Mower

Park your riding mower on solid, flat ground. Then:

1. Shut off the engine

2. Give it time to cool down fully

3. Pull out the ignition key

4. Lock the parking brake

5. Double-check that the PTO is disengaged

6. Disconnect the negative battery cable from the battery.

Step 2. Pull the Boot Off

Don't pull on the wire. Hold the rubber boot and pull it straight off the spark plug terminal. If it is stuck, gently twist it from side to side before pulling.

Step 3. Clean Around the Port

Before removal, clean away any grass, dirt, or debris around the base. Once the plug is removed, the open hole leads directly to the combustion chamber, so make sure nothing falls inside.

UDC Parts expert tip: A dry brush or a quick blast of compressed air can help clean dirt from the recessed area around the plug before removal.

Step 4. Remove the Old Plug

Attach the 5/8" socket and extension to the ratchet. Turn the spark plug counterclockwise to loosen it. Once it starts turning easily, continue removing it by hand. Avoid using power tools for this step and work slowly.

Step 5. Read the Old Spark Plug

Don't throw the old part away right away. Its condition can tell you a lot about how well your engine is running.

A healthy plug is usually dry and has a light tan or gray color. Look for these warning signs:

• Heavy black soot, which may point to incomplete combustion, a restricted air filter, a rich fuel mixture, weak ignition, or poor compression

• A wet plug, which may indicate excess fuel or oil in the combustion chamber

• Oily buildup, which may be related to worn piston rings, valve guides, a breather problem, or another engine issue

• Badly worn or rounded electrode tips

• Cracks in the ceramic insulator

• Chalky white deposits or heavy electrode erosion, which may indicate overheating

Kohler specifically recommends inspecting the plug because its deposits and electrode condition can provide clues about combustion, piston rings, valves, and carburetor operation.

If a new plug quickly develops the same problem, the spark plug itself may not be the main cause.

Step 6. Set the Gap on the New Plug

Before you start the installation, check the spark plug gap. For the Kohler KT730 example, the specified gap is: 0.030 in (0.76 mm)

Slide a wire feeler gauge through the gap. It should pass through with slight resistance.

If adjustment is needed, carefully bend only the ground electrode. Do not press against the center electrode or the ceramic insulator.

UDC Parts expert tip: The 0.030-inch gap applies to the KT730 and related engines covered by this Kohler specification. It is not a universal setting for every Cub Cadet engine, so always verify the correct specification for your machine.

Step 7. Thread the New Plug In

Always start installing the new plug by hand. This helps protect the aluminum threads inside the cylinder head. If the plug feels hard to turn from the start, remove it and try again because it may be cross-threaded. Damaging the threads in the cylinder head can lead to an expensive repair.

Once the plug is seated by hand, use a torque wrench to tighten it to the factory specification.

For the Kohler KT730, the specified spark plug torque is: 27 N·m (20 ft-lb)

Don't overtighten the plug.

Step 8. Put the Boot Back On

Push the rubber boot down over the spark plug terminal until it is fully seated. If your engine is a V-twin, repeat the same steps on the other side.

What to Do Next

Reconnect the negative battery cable, then start the engine. Listen to how it runs.

• Start smoothly without hesitation

• Idle evenly and maintain a steady speed

• Run without ignition misfires or sputtering

• Respond smoothly when the throttle is increased

• Maintain steady power while mowing

If you're still having problems after a fresh cub cadet spark plug replacement, the spark plug may not be the only cause.

A clogged air filter or stale fuel can affect engine performance, while carburetor problems may make starting and running more difficult. Weak ignition modules, loose or damaged wiring, or low compression can also cause misfires and power loss. Kohler lists these among the possible causes of hard starting, misfires, poor idle, and power loss.

Avoid replacing more parts until you identify the underlying problem.

Quick Checklist

1. Find your exact Cub Cadet model.

2. Identify the correct engine family.

3. Find the correct spark plug part number.

4. Let the engine cool completely.

5. Remove the key and set the parking brake.

6. Make sure the PTO is disengaged.

7. Disconnect the negative battery cable.

8. Pull off the rubber boot.

9. Clean dirt and debris from around the plug base.

10.  Begin the removal with a ratchet and finish by hand.

11. Inspect the old plug for wear, deposits, or damage.

12. Check and adjust the gap on the new plug if needed.

13. Thread the new plug in by hand.

14. Tighten it to the correct torque specification.

15.  Push the rubber boot firmly back onto the terminal.

16. Repeat the same steps on the other side if you have a V-twin engine.

17. Reconnect the battery.

18. Start the engine and make sure it runs properly.

Always Match the Part to Your Engine

Replacing a spark plug is a simple maintenance task, but the details matter. Always confirm your Cub Cadet model and engine type before choosing a replacement and check the correct gap and torque specifications before installation.

Keep the area around the plug clean, inspect the old plug for signs of engine problems, start the new plug by hand, and never force it into place. A correctly installed spark plug can help the mower start smoothly and maintain consistent performance.

If problems continue after replacement, check other common causes such as the air filter, fuel system, carburetor, ignition components, wiring, or compression instead of automatically replacing more parts.

Follow this order every time:

Cub Cadet model → Engine model → Spark plug part number → Gap → Torque

This helps prevent part-selection mistakes and makes spark plug replacement a simple and safe maintenance procedure.