Step-by-Step: Rebuilding Your Bomber DJ Suspension Fork

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Rebuilding the Marzocchi Bomber DJ suspension fork is an essential maintenance task to ensure peak performance and longevity. This guide will provide you with a comprehensive step-by-step approach to rebuilding the Bomber DJ suspension fork, covering everything from disassembly to reassembly, troubleshooting common issues, and optimizing performance.

Tools Required

  • 5mm, 6mm, and 8mm Allen wrenches [paid link]
  • Suspension oil (recommended by Marzocchi)
  • Wrench for the crown nut (typically 32mm)
  • Fork seal driver tool
  • Fork fluid syringe
  • Soft cloth or rag
  • Torque wrench [paid link] (up to 15 Nm)
  • Plastic container or tray for parts
  • Latex or nitrile gloves
  • Marzocchi-specific oil seals and o-rings
  • Replacement bushings (if necessary)
  • Bearing grease (high-quality)

Disassembly of the Bomber DJ Fork

Step 1: Remove the Fork from the Bike

Before beginning the rebuild process, remove the fork from the bike by loosening the headset and axle bolts. Use a 5mm Allen wrench [paid link] to remove the front wheel and brake caliper (if applicable). Set the fork aside in a stable position for the rebuild.

Step 2: Remove the Front Axle

Using the appropriate tools, remove the front axle from the fork. The Bomber DJ may have a quick-release or thru-axle system, so ensure you’re using the correct wrench or tool. Keep all components organized to prevent losing any parts.

Step 3: Unscrew the Fork’s Top Cap

Using a 6mm Allen wrench [paid link], remove the top cap from the fork. This will expose the internal spring and air valve. It’s important to note any spacers, washers, or parts under the cap as these will need to be replaced or cleaned.

Step 4: Drain the Fork Oil

With the top cap removed, invert the fork over a container to drain any oil from the damper and the lowers. Allow the oil to fully drain to avoid mixing old oil with fresh oil later in the rebuild.

Step 5: Remove the Damper Cartridge

Using a 6mm Allen wrench, unscrew the damper cartridge bolt located at the bottom of the fork legs. Once loosened, gently pull the damper cartridge out of the lowers. Be cautious of any remaining oil within the cartridge.

Step 6: Disassemble the Lower Legs

To remove the lower legs, use an 8mm Allen wrench to undo the bolts at the bottom of the fork. Once removed, slide the lower legs off the fork stanchions. Inspect the bushings, seals, and lower legs for any wear or damage that may need replacing.

Cleaning and Inspection

Step 7: Clean All Fork Components

Thoroughly clean all components, including the stanchions, damper, and lowers, with a soft cloth or rag. Be gentle when cleaning the stanchions to avoid any scratches or damage that could affect the performance of the fork. Use a suspension cleaner or mild soap and water to remove any built-up grime or debris.

Step 8: Inspect the Fork Parts

Carefully inspect each part for wear or damage. Focus on the fork seals, bushings, and internal components. Replace any worn-out seals or bushings to maintain proper fork performance. If the damper shows any signs of oil leaks or malfunctioning, consider replacing it.

Step 9: Lubricate and Prepare the Fork

Before reassembling the fork, lightly grease the stanchions, damper, and any internal parts that require lubrication. Use a high-quality suspension grease to ensure smooth movement and reduce friction. Be sure to lubricate the seals and o-rings to help them seat correctly and prevent leaks.

Reassembly of the Bomber DJ Fork

Step 10: Install New Seals and O-rings

Install new oil seals and o-rings in the fork lowers, following the manufacturer’s specifications. This is a critical step to ensure no oil leakage occurs and the fork operates smoothly. Carefully press the seals into place using a seal driver tool.

Step 11: Reinstall the Lower Legs

Slide the lower legs back onto the fork stanchions. Once aligned properly, secure them by tightening the lower leg bolts with an 8mm Allen wrench. Ensure all bolts are torqued to the manufacturer’s recommended settings, typically around 10-15 Nm.

Step 12: Reinstall the Damper Cartridge

Insert the damper cartridge back into the lowers. Use a 6mm Allen wrench to tighten the damper cartridge bolt. Ensure the cartridge is seated properly and is free of any debris. Double-check that the bolt is securely tightened.

Step 13: Add Fork Oil

Using the appropriate suspension oil recommended by Marzocchi, fill the damper and lowers. You can use a fork fluid syringe to inject the oil into the lowers. Make sure the oil level is accurate as per the manufacturer’s guidelines. Overfilling or underfilling the fork oil can affect the fork’s damping performance.

Step 14: Reinstall the Top Cap

Place the top cap back onto the fork and tighten it securely. Be sure to torque it according to Marzocchi’s specifications to prevent overtightening, which can cause damage to the internal components.

Adjusting the Bomber DJ Fork

Step 15: Set the Air Pressure

If the Bomber DJ fork uses an air spring, adjust the air pressure to match your weight and riding style. Use a shock pump to add or release air from the air chamber. Check the air pressure regularly to maintain proper suspension performance.

Step 16: Adjust Rebound and Compression Damping

After the air pressure is set, adjust the rebound and compression damping settings. These settings control how quickly the fork returns to its original position after compression and how stiff the fork feels during impact. Fine-tune these settings based on your riding preferences and terrain.

Troubleshooting Common Fork Issues

Fork Too Soft or Too Firm

  • Possible Cause: Incorrect air pressure or damping settings.
  • Solution: Adjust the air pressure to match your weight and riding conditions. Fine-tune the rebound and compression settings for a smoother ride.

Oil Leaks

  • Possible Cause: Worn seals or o-rings.
  • Solution: Replace the seals and o-rings in the lowers. Ensure that all parts are properly lubricated before reassembling.

No Compression or Rebound

  • Possible Cause: Faulty damper cartridge.
  • Solution: If the damper shows no response to adjustments, it may need replacement or a thorough service.

Optimizing Your Bomber DJ Fork Performance

Fork Sensitivity

  • Customization Tip: To enhance the sensitivity of your fork, adjust the compression damping to a lighter setting. This allows the fork to react to smaller bumps more effectively.

Weight Adjustment

  • Customization Tip: If you’re looking for improved bottom-out resistance, you can increase the air pressure slightly. Conversely, lowering the air pressure can enhance comfort but may reduce bottom-out protection.

Upgrade Options

  • Customization Tip: Consider upgrading to a more advanced damper cartridge if you seek improved control and responsiveness. The Bomber DJ can be tuned with different spring rates and dampers to tailor the ride feel to your specific needs.

Conclusion

Rebuilding the Marzocchi Bomber DJ suspension fork is a vital skill for maintaining its performance over time. By following the steps outlined in this guide, you can ensure that your fork operates at its best, providing excellent suspension, comfort, and control on all types of terrain. Regular maintenance and adjustments will extend the life of your fork, ensuring that your rides are smooth and responsive.