If your home is situated on a large piece of property, your lawn is exceptionally spacious, or you’re a professional landscaper, you likely depend on a riding mower or a zero-turn mower when cutting grass. As convenient (and even fun!) as it may be to steer this equipment around the yard, these mowers have their own unique ways of malfunctioning. One of these is the failure of a riding mower to properly engage the blades to do the actual mowing.
In this article, Repair Clinic.com will help you investigate the most likely reasons why your riding lawn mower’s cutting blades are not spinning. As always, the first step to successfully troubleshoot the cause of the problem is understanding how the equipment does what it does when all the components are working together properly.
Understanding how a riding mower’s cutting blades work
The main advantage of a riding mower compared to a walk-behind mower is the increased size of the mower’s deck which can accommodate multiple cutting blades to cut through a wider swath of grass with fewer passes.
The width of the deck determines the number of cutting blades
The deck on a riding mower supports spindles that the blades and pulleys are attached to. The number of blades used will depend on the cutting width of the deck and the length of the blades themselves. For example, a thirty-inch cutting width will only require one blade while a cutting width of forty-two inches or more will require two or three blades. To ensure all the grass is cut evenly beneath a wider mower deck, the blades are slightly staggered so the cutting area between each blade is overlapped by the blades. This overlap is important, so you should be careful not to grind too much off the ends of the blades when sharpening. If the grass in-between the blades are being left uncut, you’ll know it’s time to replace the old blades with new ones.
What makes the cutting blades spin?
Riding lawn mowers usually have an engine shaft fitted with a double pulley that will transfer engine power to the transmission and the cutting blade deck by two separate belts. For riding mowers using a manual clutch, the mower blades are engaged by manually shifting a lever that moves a pulley assembly to tighten the blade drive belt. The rotating engine shaft will then drive the belt, which in turn, rotates the pulleys to spin one or more cutting blades. If the riding mower uses an electric power take off (or PTO for short) clutch, a clutch solenoid is energized by actuating a power take off switch. Once the solenoid is energized, the PTO clutch will directly engage the drive belt to rotate the cutting blades.
5 reasons why your riding mower’s blades won’t engage
If your riding lawn mower cutting blades aren’t engaging, here are the five most likely defective parts you should inspect:
- Defective PTO clutch components – As noted earlier, on models with an electric power take off (PTO) clutch, once the clutch solenoid is energized, the clutch will engage the drive belt to rotate the blades. If the PTO clutch is not receiving power, the clutch solenoid is defective, or the clutch itself is worn out, the blades will not engage. Since a PTO clutch is not repairable, you will need to replace a broken or worn out clutch with a new one.
- Faulty PTO switch – If the power take off (PTO) switch is faulty, it can stop voltage from reaching the clutch and prevent the blades from engaging. To help determine if the PTO switch is faulty, you can use a multimeter to test the switch for electrical continuity – a continuous electrical path present in the switch. If the PTO switch tests negative for continuity in the “on” position, it is defective and will need to be replaced.
- Worn-out manual clutch – On riding mower models using a manual clutch, the clutch lever could be damaged or the clutch itself could be worn out, preventing the component from moving the pulley assembly to tighten the blade drive belt to engage the blades. If this is the case, you will need to install a new clutch assembly to resolve the issue.
- Worn or broken blade drive belt – The blade drive belt may be worn or broken and unable to engage the blades. If the belt is intact, inspect it to see if it’s loose or slipping on the pulleys then replace it with a new one if necessary.
- Damaged clutch cable – The cable that controls the manual clutch could be damaged or misaligned as well, or the tension spring attached to the cable could be broken. Realigning or replacing the cable with a new one should solve the problem.
Finding the resources to fix your riding mower yourself
Where can you find the step-by-step instructions to install a new blade drive belt or a new clutch cable on your riding mower? Visit Repair Clinic.com and explore the “Videos & Articles” section of the website. As your repair partner, Repair Clinic provides you with thousands of troubleshooting and procedural videos, step-by-step guides, diagrams, schematics, and articles so you’ll have the knowledge and confidence to take on the repair yourself, whether you’re fixing lawn and garden equipment, home appliances, or heating and cooling units.
Shop Repair Clinic for genuine manufacturer riding mower parts
In addition to a wealth of free repair help content, Repair Clinic stocks genuine OEM riding lawn mower parts direct from manufacturers like Craftsman, Cub Cadet, Exmark, Husqvarna, Ryobi, Troy-Bilt, and many more, that can be shipped to you quickly. Enter the full model of the riding mower in Repair Clinic’s “Shop Parts & Get Answers” search bar, or the engine model number if you’re searching for an engine component, to see a complete list of replacement parts compatible with your mower. You can then use the “Part Category” filter (example: “Transmission, Brake & Clutch”) along with the “Part Title” filter (example: “Clutch Cable”) to refine that initial part list to locate the exact manual clutch, clutch cable, blade drive belt, or PTO switch you need. Partner up with Repair Clinic to save yourself time and money while keeping your riding mower in top condition.