KTM 85 SX Gearing Recommendations
For the KTM 85 SX (and its siblings, the Husqvarna TC 85 and GasGas MC 85), the most common combination depends on the wheel size, as the "Small Wheel" and "Big Wheel" versions use different factory gearing to compensate for the different rear tire diameters.
Regardless of the sprocket teeth, all modern 85cc models from these brands use a 428 pitch chain.
1. Standard (Stock) Gearing
Most riders stick with the OEM (Original Equipment Manufacturer) ratios because KTM tunes them specifically for the powerband of the 85cc engine.
| Wheel Setup | Front Sprocket | Rear Sprocket | Chain Length |
| Small Wheel (17"/14") | 13 Tooth | 46 Tooth | 124 Links |
| Big Wheel (19"/16") | 13 Tooth | 49 Tooth | 124–126 Links |
2. Most Common Performance Adjustments
Riders often change their gearing to suit specific track conditions or to help the bike stay "on the pipe" (in the powerband) more easily.
For Better Acceleration (Snappier):
The Setup: Go down 1 tooth on the front (12T) or up 1-2 teeth on the rear (47T or 48T for Small Wheel).
Why: This is popular for tight, technical tracks or for riders who need more "grunt" coming out of corners without having to abuse the clutch.
For Higher Top Speed (Desert/Open Tracks):
The Setup: Go up 1 tooth on the front (14T) or down 2-3 teeth on the rear.
Why: This stretches out the gears, allowing the bike to reach a higher speed in each gear. This is common for wide-open sand tracks or cross-country racing.
3. Recommended Materials
Since 85cc bikes are high-revving and often ridden in mud and sand, the material of the chain and sprockets matters for longevity:
Chain: Look for a 428 Heavy Duty (HD) or Gold Non-O-Ring chain. While O-ring chains last longer, many 85cc racers prefer non-O-ring chains because they have less "drag," allowing the small engine to spin the wheel more freely.
Front Sprocket: Always use Case-Hardened Steel (like the Renthal Grooved series).
Rear Sprocket: Aluminum (lightweight for racing) or Twin-Ring/Hybrid (steel teeth with an aluminum inner) for the best balance of weight and 3x the life of standard aluminum.