Stihl 3/8" Picco 6 Tooth Spur Sprocket Kit - MS251, MS241C-M

Restore original factory torque, positive power transfer, and structural cutting efficiency to your mid-range chainsaw with the genuine OEM STIHL 3/8" Picco 6-Tooth Spur Sprocket Assembly. Precision-manufactured under factory part number 1143 640 2000, this high-strength structural clutch drum shell is an exact drop-in structural replacement engineered specifically for modern 1143-series engines, including the MS 231, MS 251, and professional M-Tronic MS 241 C-M powerheads. Replacing a grooved, heavily pocketed, or out-of-round drive drum remedies erratic clutch slipping, stops immediate chain stalling under heavy structural loads, and optimizes cutting throughput.

The core design advantage of this original equipment manufacturer layout lies in its highly durable, single-piece spur architecture. The 6-tooth Picco (Low Profile) configuration is precision-machined directly onto the exterior of the case-hardened alloy drum shell, ensuring maximum rigid structural integrity and direct mechanical link-to-clutch contact. By utilizing a 6-tooth gear ratio, this drum maximizes internal engine leverage and mechanical torque, preventing your powerhead from bogging down in dense hardwoods while maintaining consistent, stable chain speed across the guide bar's rails.

True OEM Engineering vs. Soft Aftermarket Metal: Chainsaw drive sprockets function under extreme centrifugal forces and high thermal stress. Low-grade aftermarket replica drums frequently suffer from out-of-round concentricity errors, causing severe crankshaft vibration, rapid wear on internal clutch shoes, and premature failure of the integrated oiler drive mechanism. This genuine STIHL spur sprocket features precision-ground interior bore tolerances to guarantee exact seating on your crankshaft's needle cage bearing, ensuring a long service life cycle and stable, continuous oil pump engagement at peak operating RPMs.

Configuration & Application Profile: Designed exclusively for STIHL 1143-series powerheads configured with a 3/8" Picco (Low Profile / Extended Cut) guide bar and chain loop assembly. This drum will not accept 3/8" Standard Full Profile, .325", or 1/4" pitch chain configurations. Packaged as a single, fully integrated spur sprocket and clutch drum shell unit (needle cage bearing available separately).

Key Features & Benefits

• Direct Single-Piece Spur Architecture: Features a fixed 6-tooth Picco gear machined directly to the drum shell, eliminating secondary loose components or structural flex.
• High-Torque 6-Tooth Profile: Maximizes mechanical engine leverage and power delivery when bucking dense hardwoods or felling utility timber.
• 100% Genuine OEM STIHL Manufacture: Built from premium, heat-treated high-carbon steel alloy designed specifically to withstand harsh commercial and property-maintenance environments.
• Precision Oiler Drive Integration: Explicitly notched to interface seamlessly with the internal automatic oil pump drive gear for continuous, high-RPM bar lubrication.
• Concentric Anti-Vibration Design: Precision-ground manufacturing tolerances minimize radial runout, protecting your engine's crankshaft and main bearings from structural stress.
• Full Variant Fitment Support: Perfectly compatible with standard engine configurations as well as specialized ErgoStart and Quick Chain Adjusting (C-BE) models.

Technical Specifications & System Components