The 2012 Suzuki RM85 is a popular motocross bike for young and intermediate riders, known for its peppy engine and capable chassis. One of the most critical components for handling and rider comfort is the front fork suspension system. Over time, seals wear, bushings develop clearance, and oil degrades, leading to poor damping, stiction, or leaks. This guide covers the essential front fork suspension parts for the 2012 RM85, from standard replacement items to performance upgrades, helping you make informed decisions for maintenance or improvement.
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Understanding the 2012 RM85 Front Fork System
The 2012 RM85 uses a Showa 36mm inverted telescopic fork with a fully adjustable damping system. It has approximately 11.4 inches of travel and features a spring preload adjuster, compression damping adjuster, and rebound damping adjuster. The fork operates with two springs: a main spring on each leg and a small spring for the cartridge system. The stock spring rates are 0.41 kg/mm (standard) but may vary slightly depending on the market.
Common Wear and Tear Symptoms
Typical signs that your RM85 front fork needs attention include:
- Leaking fork seals – oil appearing on the fork tubes, often accompanied by dust accumulation.
- Stiction or binding – the fork feels harsh or stick when moving through its travel.
- Reduced damping – the fork bottoms out easily or feels bouncy.
- Excessive play – if the bushings are worn, you may feel a clunk when hitting bumps.
Essential Front Fork Suspension Parts for Replacement
When servicing the 2012 RM85 front forks, the following parts are commonly replaced:
Fork Seals and Dust Wipers
Fork seals are the primary line of defense against dirt and oil loss. For the 2012 RM85, the OEM seal is a 36mm single-lipped seal. Aftermarket options from brands like All Balls, SKF, and Pivot Works offer double-lipped designs for better longevity. Dust wipers (aka foam wipers) should be replaced simultaneously to keep debris from scratching the fork tube. Always use a seal driver and apply a thin layer of grease to the inner lip during installation.
Bushings (Inner and Outer)
The inner and outer bushings slide along the fork tube and lower leg, providing low-friction movement. Worn bushings create clearance that leads to stiction or wobble. OEM bushing part numbers are 51190-27R00 (inner) and 51198-27R00 (outer). Aftermarket kits often include both. Measure the clearance with a feeler gauge; if it exceeds 0.006 inches, replace them.
Springs
Stock springs are set for an average rider of about 140 lbs. If you are heavier or lighter, or if you want a plusher ride, consider swapping to a different spring rate. Common aftermarket spring brands are Race Tech, Cannon, and eibach. For motocross, rates from 0.38 to 0.45 kg/mm are typical. Changing springs requires disassembling the fork and replacing both springs.
Fork Oil and Recommended Viscosity
Fork oil lubricates the internal components and provides damping resistance. The stock oil weight is 5wt, but many riders prefer 5wt or 7wt for deeper tuning. Capacity is about 340ml per leg (measured from fully collapsed without spring). Always check the air gap after filling: typically 95mm from the top of the tube with the spring removed for a standard setting. Using the wrong viscosity can make the fork too soft or too stiff.
Upgrading the 2012 RM85 Front Fork
If you want to improve the fork's performance beyond stock, consider these upgrades:
Performance Valve Kits
Valve kits replace the stock damping pistons with adjustable or improved designs. The most popular is the Race Tech Gold Valve kit, which allows precise tuning of compression and rebound damping. These kits require installing new valving and often involve drilling or reaming the existing piston. They provide a wider range of adjustability and better bottoming resistance.
Spring Rate Changes
Even if you don't replace the valves, changing the spring rate to match your weight and riding style is one of the most cost-effective upgrades. Race Tech's spring rate calculator suggests 0.48 kg/mm for a 160 lb rider on motocross. Use a spring that is linear rather than progressive for consistent performance.
Complete Fork Rebuild Kits
Several aftermarket companies offer complete rebuild kits that include seals, bushings, dust wipers, and sometimes even new springs or valve parts. These kits simplify ordering and ensure all wear items are replaced together. Wiseco and All Balls make specific kits for the 2012 RM85. They are a good choice for a full overhaul.
Step-by-Step Fork Rebuild Considerations
Rebuilding the front forks of a 2012 RM85 requires careful disassembly and accurate assembly. Here are key points:
Tools You'll Need
- Fork seal driver (36mm)
- Fork tube wrench or 14mm and 17mm sockets for the top cap
- Metric hex keys (4mm, 5mm, 6mm)
- Oil measuring cup and syringe for air gap
- Plastic hammer to drive seals without damage
- Clean work area to avoid contamination
Disassembly and Inspection Tips
Start by removing the front wheel, fender, and brake caliper. Loosen the fork tube pinch bolts and pull the forks off. Drain the oil from the bottom, then disassemble by compressing the fork and removing the top cap first (watch the spring). After removing the spring, slide off the outer tube. Inspect the fork tube for scratches or pitting; if damaged, replacements may be needed as no seal will hold.
Reassembly and Oil Fill Procedure
Install new bushings by pressing them into the outer tube until flush. Lightly grease the seal lip before sliding the inner tube through the new seal. Use the seal driver to seat the seal properly. Fill with oil to the specified height (95mm typical), then slowly cycle the fork to burp air. Reinstall the spring and top cap, watching the correct orientation of the spring seat. Torque the top cap to 50 lb-ft.
Final Recommendation
For a 2012 RM85 that is used regularly, a basic rebuild with new seals, bushings, and oil is a must every 20–30 riding hours. If you notice performance issues like bottoming or harshness, address the spring rate first before investing in expensive valve kits. For racers or heavier riders, a spring change paired with a high-quality valve kit like the Gold Valves will provide significant improvements in control and comfort. Stick with reputable brands such as All Balls, SKF, or Race Tech, and always follow the service manual's torque and oil specs. The result is a front end that inspires confidence and lets you focus on the track, not the suspension.