The average life expectancy of a walk-behind lawn mower is eight to ten years, provided you perform regular maintenance like annual tune-ups and periodic oil changes. But what do you do if the mower self-propel system fails while the mower’s engine is still in great shape and the cutting blade is still delivering a precision cut? You don’t want to junk the equipment, but you’re also not happy that your walk-behind mower is now a cumbersome “push” mower.
Repairing the lawn mower self-propel function may be easier than you think. In this article, we’ll highlight the five most likely reasons why your mower’s self-propel feature is no longer working and how to fix it. Let’s start with how that self-propel system actually works.
How the lawn mower self-propel system works
The lawn mower engine crankshaft extends out the bottom of the crankcase where it, ultimately, connects to the mower’s blade or blades under the deck. However, on walk-behind mowers that have a self-propel function, the engine crankshaft will first connect to a self-propel drive pulley.
A belt is looped around the drive pulley attached to the crankshaft as well as another pulley mounted on a gearbox or transmission. When the drive arm or bail arm is held, a control cable and spring assembly applies tension to this second pulley which allows the belt to turn the gears to rotate the axle to self-propel the mower’s front or rear wheels. Typically, the engine will automatically increase torque as needed to maintain a consistent speed while the grass is being cut. Once the drive lever or bail arm is released, the self-propel function ceases.
5 reasons why your lawn mower’s wheels aren’t being self-propelled
If, after you engage the drive lever or bail arm, the mower does not self-propel, here are five probable causes you should investigate and what you can do to resolve the problem:
- Worn wheel assembly – The lawn mower wheel assembly will often have drive teeth that engage with the transmission gear. If the teeth are worn out, the transmission won’t be able to drive the wheels. You can resolve this issue by replacing the old wheel assembly with a new one.
- Broken V-belt – On some models, a V-belt rotates the drive pulleys to turn the axle. If the V-belt is worn or broken, the wheels won’t turn. Inspect the V-belt for damage and replace it with a new one if necessary.
- Damaged control cable – A broken, or misadjusted, control cable will prevent the mower from self-propelling as well. If the cable is intact but doesn’t move freely, you can try applying a small amount of lubrication to the cable. However, if the part appears kinked or twisted, you should go ahead and replace the cable with a new one.
- Defective transmission – The lawn mower transmission is powered by the V-belt which connects to the engine crankshaft. If the transmission pulley spins when the mower is running, but the wheels don’t turn, the transmission is likely defective and will need to be replaced.
- Damaged drive pulley – The transmission drive pulley itself can become damaged and be unable to engage the wheel assembly. Inspect the pulley for damage and replace if necessary.
Shop Repair Clinic for genuine manufacturer lawn mower parts
Now that you’ve completed troubleshooting the lawn mower, do you need to replace the V-belt? Or maybe the control cable, pulley, or transmission? Repair Clinic.com – your repair partner – has this next step covered. Locate the model number label on your mower, which may be found attached to the deck behind the engine, on the left-or-right side of the deck, or on the back of the deck under the rear guard. Write the whole model number down (or take a photo with your smartphone) and enter that number in the Repair Clinic website search bar. The resulting list will show you all the compatible parts associated with your specific mower, genuine manufacturer parts from such top names as Craftsman, Honda, Husqvarna, Murray, Snapper, Troy-bilt, Toro, and more. You can then use the “Part Category” filter (“Control Cable”, “Belt”) along with the “Part Title” filter (“Traction Control Cable”, “V-Belt”) to narrow that initial part list down to the exact cable, belt, pulley, or transmission you need.
But the support doesn’t stop there. You’ll find hundreds of model-specific “how-to” videos, diagrams, schematics, and articles on the Repair Clinic site that will show you, step-by-step, the proper procedure to replace that old belt, cable, or wheel assembly with a new one. Partner up with Repair Clinic to save yourself some time and money while keeping your lawn mower self-propelling for years to come.