Stihl 3/8" 7 Tooth Spur Sprocket - MS311, MS391

Restore max power transfer, crisp clutch engagement, and original cutting smoothness to your heavy-duty STIHL chainsaw with the Genuine OEM STIHL 3/8" 7-Tooth Spur Chain Sprocket Drum Assembly. Precision-engineered under factory part number 1140 640 2000 (1140-640-2000), this heavy-duty, one-piece spur sprocket and clutch drum unit is an exact direct-fit replacement designed to swap out grooved, worn, or heat-damaged drive sprockets on 1140 series powerheads like the MS 311 and MS 391. Installing a fresh factory spur sprocket eliminates erratic chain chatter, prevents severe drive link burring, and stops clutch slippage during heavy wood cutting.

Featuring a standard 7-tooth (7T) drive spur profile calibrated specifically for full-size 3/8" pitch guide bars and saw chains, this drive drum maximizes pulling force on high-displacement mid-range engines. Crafted as a single, solid-forged steel component, the integral drive teeth are induction-hardened to resist intense frictional wear and bar oil contamination. Its internal drum bore and oiler drive notch interface seamlessly with your saw's clutch shoes, needle bearing, and oil pump drive system for immediate, trouble-free operation.

True Genuine OEM Manufacturing vs. Cheap Aftermarket Drums: High-torque 70cc-class family powerheads subject drive drums to immense rotational stress. Low-cost aftermarket spur drums frequently suffer from out-of-round machining, soft metal spur teeth that groove rapidly, and out-of-spec drum walls that lead to premature clutch pad wear or excessive vibration. Genuine STIHL drive components guarantee exact dynamic balance, precise needle bearing fitment, and long-lasting commercial reliability.

Configuration & Fitment Profile: Factory-designed for 1140 chassis STIHL powerheads running standard 3/8" pitch cutting setups. Direct replacement for the clutch drive and oil pump drive systems across the MS 311 and MS 391 powerhead series. Needle bearing sold separately.

Key Features & Benefits

• 100% Genuine OEM STIHL Manufacture: Built to exact factory specifications using high-density, heat-treated structural steel alloys to guarantee proper fitment and maximum service life.
• High-Torque 3/8" Pitch 7-Tooth Gearing: Delivers maximum pulling power through dense hardwoods, large log bucking, and heavy felling operations.
• Induction-Hardened Steel Spur Teeth: Precision-ground drive spurs resist premature grooving, keeping chain drive links meshing smoothly and safely.
• Integral One-Piece Drum Design: Combines the clutch drum and drive sprocket into a single rigid unit for simple, drop-in replacement during routine maintenance.
• Precision 1140 Oiler Interface: Features exact drive notch geometry that engages smoothly with the oiler drive wire on MS 311 and MS 391 models for continuous bar lubrication.

Technical Specifications & Master Fitment Chart