KTM 85 SX Parts Guide

KTM 85 SX: The Ultimate Tech & Spec Guide

The KTM 85 SX is the benchmark for amateur motocross. Whether you are maintaining a practice bike or tuning a race machine, knowing your exact generation is critical for ordering the right parts. Below is your definitive map to the 85cc class leader.

🛠 Model Generations & Compatibility

To ensure you buy the right parts, identify which "Generation" your bike belongs to. The 85 SX has four distinct eras.

Generation Year Range Key Characteristics
Gen 1 2004 – 2012 The "Original." Steel frame, older styling, Formula brakes.
Gen 2 2013 – 2017 Major Update. Sharp bodywork, revised engine, Formula brakes, traditional spring forks.
Gen 3 2018 – 2024 The "Air" Era. Lighter engine, new frame, and WP AER 43 Air Forks.
Gen 4 2025 – Present New Chassis. New frame geometry, one-piece swingarm, and side-mount rear shock.

⛽ Factory Jetting Specs (Stock Baseline)

Note: These are baseline specs for Sea Level at 70°F. Always adjust for your local altitude and temperature.

2018 – 2024 Models (Gen 3)

  • Carburetor: Keihin PWK 28
  • Main Jet: 142 - 145 (Stock is often 142)
  • Pilot Jet: 45
  • Needle: NRKC
  • Clip Position: 3rd from top
  • Air Screw: 1.5 - 2.0 turns out

Tech Note: The 2018+ engine flows more air, requiring a significantly larger main jet than older models. Do not use older specs on these bikes!

2004 – 2017 Models (Gen 1 & 2)

  • Carburetor: Keihin PWK 28
  • Main Jet: 118 - 120
  • Pilot Jet: 45
  • Needle: N5HG
  • Clip Position: 3rd from top
  • Air Screw: 1.5 turns out

⚙️ Gearing & Chain Specs

The KTM 85 SX uses a standard 428 Pitch Chain. Sprocket sizes depend on your wheel size.

  • Front Sprocket: 13 Tooth (Standard)
  • Rear Sprocket (Small Wheel 17/14): 46 Tooth
  • Rear Sprocket (Big Wheel 19/16): 49 Tooth
Racer's Tip: For deep sand or mud, go +1 or +2 teeth on the rear (e.g., 48T on a Small Wheel) to help the bike pull through the heavy terrain without bogging.

💡 Critical Maintenance Tips

1. The Power Valve (2018+ Models)

The "Gen 3" engine features an adjustable diaphragm-style power valve. If the bike feels "flat" or lacks hit, check the adjustment screw. Turning it IN delays the hit (milder); turning it OUT opens it sooner (aggressive).

2. WP AER 43 Air Pressure

If you ride a 2018 or newer model, you must check fork air pressure before every ride using a digital fork pump.

  • Stock Pressure: ~5.0 Bar (73 PSI)

3. Piston Intervals

Because the 85 SX revs higher than 125s, piston wear is accelerated.

  • Racing: Replace every 15–20 hours.
  • Practice/Play: Replace every 30–40 hours.

Shop KTM 85 SX Parts

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