Introduction
This manual provides essential information for the safe and effective use, installation, and maintenance of your Oregon 91-591 Mower Blades. These blades are designed as a replacement for Jacobsen Part # 4137186, suitable for 90-inch cut systems. Please read all instructions carefully before proceeding with installation or operation.
Setup and Installation
Safety First: Always disconnect the spark plug wire or remove the battery before performing any maintenance or installation on your mower to prevent accidental starting.
- Prepare the Mower: Park the mower on a flat, stable surface. Engage the parking brake. Ensure the engine is off and cool. Disconnect the spark plug wire or remove the battery.
- Access Blades: Carefully tilt the mower onto its side, ensuring the carburetor and air filter are facing upwards to prevent fuel or oil leaks. Alternatively, raise the mower using a suitable lift or jack, ensuring it is securely supported.
- Remove Old Blades: Wear heavy-duty gloves for protection. Use a wrench or socket to loosen the blade retaining nut. You may need a block of wood to prevent the blade from turning while loosening the nut. Remove the old blade and retaining hardware. Note the orientation of the old blade for correct installation of the new blade.
- Inspect Components: Examine the blade spindle, washers, and bolts for wear or damage. Replace any worn or damaged parts before installing new blades.
- Install New Blades: Position the new Oregon 91-591 blade onto the spindle, ensuring the cutting edge faces the correct direction (typically upwards towards the mower deck). The blade's lift should be oriented to create airflow for proper grass discharge. Secure the blade with the retaining nut and washers.
- Tighten Fasteners: Tighten the blade retaining nut to the manufacturer's specified torque. Refer to your mower's owner's manual for exact torque specifications. Overtightening or undertightening can be dangerous.
- Repeat for All Blades: If replacing multiple blades (this product comes in a 3-pack), repeat the process for each blade.
- Final Check: Once all blades are installed, lower the mower, reconnect the spark plug wire or battery, and perform a visual inspection to ensure all components are secure.
An image of the Oregon 91-591 mower blade, showing its shape and center hole. This illustrates the typical appearance of the blade for installation reference.
Operating Instructions
After installing new blades, follow these general operating guidelines for safe and effective mowing:
- Pre-Mow Inspection: Before each use, inspect the blades for any signs of damage, bending, or looseness. Ensure all nuts and bolts are tight.
- Clear Debris: Always clear the mowing area of any rocks, sticks, wires, or other debris that could be struck by the blades.
- Proper Mowing Height: Adjust your mower's cutting height according to grass type and conditions. Avoid cutting more than one-third of the grass blade length at a time for optimal lawn health.
- Safe Operation: Operate the mower at a safe speed. Never operate the mower without the discharge chute or grass catcher in place. Keep hands and feet away from rotating blades.
- Blade Balance: If you notice excessive vibration during operation, stop the mower immediately and check the blades for balance. An unbalanced blade can cause damage to the mower and produce an uneven cut.
Maintenance
Regular maintenance of your mower blades ensures optimal cutting performance and extends their lifespan.
- Cleaning: After each use, clean grass clippings and debris from the blades and underside of the mower deck. Built-up grass can reduce cutting efficiency and promote rust.
- Sharpening: Sharpen blades regularly, typically after every 8-10 hours of use, or more frequently if you notice a ragged cut or dull edges. Use a blade sharpener or file, maintaining the original cutting angle.
- Balancing: After sharpening, always check the blade for balance. An unbalanced blade can cause excessive vibration, leading to premature wear on mower components and an uneven cut. Use a blade balancer tool to ensure proper balance.
- Inspection for Damage: Periodically inspect blades for cracks, bends, or excessive wear. If a blade is severely damaged, bent, or has cracks, it must be replaced immediately. Do not attempt to repair damaged blades.
- Storage: If storing the mower for an extended period, clean and lightly oil the blades to prevent rust.
Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Uneven or ragged cut | Dull blades, bent blades, unbalanced blades, incorrect cutting height. | Sharpen or replace blades. Check for bends and balance. Adjust cutting height. |
| Excessive mower vibration | Unbalanced blades, bent blades, loose blade retaining nut. | Balance or replace blades. Check for bends. Tighten blade retaining nut to specifications. |
| Poor grass discharge/clogging | Dull blades, excessive grass buildup under deck, mowing wet grass. | Sharpen blades. Clean under deck. Avoid mowing wet grass. |
| Blades not spinning freely | Obstruction, seized spindle, incorrect installation. | Remove obstruction. Inspect spindle for damage. Reinstall blades correctly. |
Specifications
These specifications apply to the Oregon 91-591 Mower Blade (3-pack) designed to fit Jacobsen Part # 4137186 for 90-inch cut systems.
- Oregon Part Number: 91-591
- Replaces Jacobsen Part Number: 4137186
- Quantity: 3 blades per pack
- Cut System Compatibility: 90-inch cut
- Length: 22-5/16 inches (56.67 cm)
- Center Hole Diameter: 1/2 inch (1.27 cm)
- Width: 2.50 inches (6.35 cm)
- Thickness: 0.250 inches (0.635 cm)
- Lift: 1-1/8 inches (2.86 cm)
- Offset: 1/8 inch (0.32 cm)
Warranty and Support
For specific warranty information regarding your Oregon 91-591 Mower Blades, please refer to the documentation included with your purchase or visit the official Oregon website. If you require technical assistance or have questions not covered in this manual, please contact Oregon customer support directly. Keep your purchase receipt as proof of purchase for any warranty claims.
