SuperSprox Orange Stealth Rear Sprockets for KTM, Husqvarna & GasGas

The Supersprox Stealth Rear Sprocket (RST-990 series) is a hybrid-material 520 drive sprocket engineered for off-road, cross-country, and motocross motorcycles. Standard drive options present an inherent compromise: 7075-T6 all-aluminum sprockets offer low rotating weight but wear out rapidly under abrasive mud and chain grit, while solid steel sprockets offer high longevity at the cost of substantial unsprung rotating mass.

The Stealth architecture resolves this trade-off by joining an induction-hardened, high-carbon steel outer tooth ring to an aircraft-grade 7075-T6 aluminum inner carrier using permanent high-strength stainless steel rivets. The outer steel teeth deliver up to three times the operating lifespan of an aluminum sprocket and resist chain hook formation under heavy throttle loads. The CNC-machined 7075-T6 aluminum inner core reduces rotational mass by roughly 50% compared to a solid steel unit, decreasing gyroscopic inertia to maintain light suspension action and crisp throttle response.

Features:

• Hybrid Bi-Metal Architecture: Combines high-carbon steel outer teeth for extended wear resistance with a 7075-T6 aluminum carrier for reduced rotational mass.

• Extended Wear Life: Delivers up to three times the service life of an all-aluminum rear sprocket under abrasive off-road mud and sand conditions.

• Rotational Weight Reduction: Approximately 50% lighter than a standard all-steel sprocket, reducing unsprung inertia at the rear wheel.

• High-Strength Riveted Construction: Outer ring and inner carrier are secured using patented inter-locking geometry and high-tensile stainless steel rivets.

• Self-Cleaning Tooth Profile: Machined mud grooves between teeth channel trail silt, clay, and sand outward from the chain rollers to minimize driveline tension spikes.

• Corrosion-Resistant Finish: Anodized aluminum inner core with electro-plated protective coating on the steel tooth ring.

What's in the Box:

• 1x Supersprox Stealth 520 Rear Sprocket (RST-990 Series)

• (Note: Sprocket mounting bolts sold separately. Select required tooth count and inner carrier color from the variant dropdown before checkout).

Fitment:

• 1991–2027 – KTM 125–500cc EXC-F, XC-W, XCF-W, XC, XC-F, SX, SX-F
• 2014–2027 – Husqvarna 125–501cc FE, TE, FX, TX, FC, TC
• 2021–2027 – GasGas 125–500cc EC-F, EC, EX-F, EX, MC-F, MC
• 2000–2014 – Husaberg 125–570cc TE, FE, FX

Fitment Notes:

• Chain Pitch: Standard 520 drive chain.

• Mounting Pattern: Standard KTM 6-bolt pattern (150 mm bolt circle diameter / 125 mm inner hub register / M8 countersunk bolt holes).

• Incompatible Platforms: DoesNOT fit KTM 690 Enduro / Husqvarna 701 Enduro / GASGAS 700 ES (larger 6-bolt hub pattern), or KTM 790/890/1090/1190/1290 Adventure platforms.

• Sprocket Bolt Torquing Technique: Never tighten sprocket bolts from the bolt head side. The countersunk Allen or Torx head should be held completely stationary with a bit while you tighten and torque the nut on the inside of the wheel hub flange. Rotating the tapered countersunk bolt head against the sprocket chamfer can gall the aluminum recess and cause false torque readings. Clean all hub threads, use medium (blue) threadlocker on the threads, and torque the M8 nuts to the factory specification of35 Nm (25.8 ft-lbs) in a criss-cross star pattern. Always replace worn locking nuts when mounting a new sprocket.

   

• Pairing with New Chains: Installing a new Supersprox Stealth rear sprocket on a worn or stretched drive chain will prematurely ruin the steel teeth. As a drive chain stretches, its pitch spacing increases, concentrating the entire drive load onto the tip of a single sprocket tooth rather than distributing it evenly across the bottom of the tooth valley. Always measure chain elongation across 20 links or install a new front countershaft sprocket and quality sealed 520 chain at the same time to maximize drivetrain longevity.

   

• Gearing Changes & Chain Guide Clearance: Moving up in tooth count (e.g., swapping a stock 48T or 50T to a 51T or 52T for technical singletrack) shifts the rear axle forward in the swingarm swing block slots and increases the overall sprocket diameter. Verify that the lower chain guide has adequate vertical and lateral clearance for the larger sprocket radius; on 51T and 52T sprockets, lower chain guide wear blocks may need to be adjusted or set back to prevent the chain rollers from dragging heavily against the guide housing.

Part Number: RST-990