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The new B Series track feller bunchers feature smoother hydraulic performance, increased engine HP, a more comfortable operator station and better right side operator visibility. The Cat 521B Series are zero tail swing machines designed for medium to high production clear cut and or select cut on rough terrain. These machines perform in a variety of small through larger tree size applications. A robust undercarriage utilizes proven components, customized for demanding forestry conditions. The unique boom design provides industry leading lift capacity throughout full reach range, a benefit in large timber.


  • Gross Power 303.0 HP 226.0 kW

Hydraulic System

  • Pumps (3) Electric hydraulic oil fill pump Electric hydraulic oil fill pump
  • Pumps (2) Dedicated variable displacement pump for boom and implement functions - 200 cc Dedicated variable displacement pump for boom and implement functions - 200 cc
  • Pumps (1) Dedicated variable displacement pump for travel circuit - 200 cc Dedicated variable displacement pump for travel circuit - 200 cc

Operating Specifications

  • Maximum Reach - With Head 32.5 ft 9.9 m

Service Refill Capacities

  • Engine Oil 10.3 gal (US) 39.0 l
  • Swing Drive 2.6 gal (US) 10.0 l
  • Hydraulic System 118.0 gal (US) 448.0 l
  • Cooling System 10.8 gal (US) 41.0 l
  • Fuel Capacity 226.0 gal (US) 856.0 l


  • Operating Weight - Without Head 59450.0 lb 26966.0 kg


  • Cab Cab meets FOPS/OPS/ROPS/WCB/OR-OSHA requirements Cab meets FOPS/OPS/ROPS/WCB/OR-OSHA requirements


  • Size 330 EX (D7) 330 EX (D7)
  • Pitch 8.5 in 215.9 mm

Power Train

  • Displacement 537.0 in³ 8.8 l
  • Rated Power - 2,100 rpm 282.0 HP 210.3 kW
  • Gross Power - 1,800 rpm 303.0 HP 226.0 kW
  • Gross Power 303.0 HP 226.0 kW
  • Engine Model Cat® C9 ACERT™ Cat® C9 ACERT™

Boom System

  • Track Harvester Configuration - Lift Over Front of Tracks: Maximum Reach - With head 32.5 ft 9.9 m
  • Track Harvester Configuration - Lift Over Front of Tracks: Bare Pin Lift at Maximum Reach - Without Head 4000 kg @ 9.8 m (8,800 lb @ 32 ft 5 in) 4000 kg @ 9.8 m (8,800 lb @ 32 ft 5 in)

Operating Weights - Without Heads, Standard Counterweight

  • Track Harvester Configuration - 521B 59450.0 lb 26966.0 kg

Track Gauge

  • 521B 102.0 in 2591.0 mm

Track Length

  • Track Length 191.1 in 4855.0 mm

Ground Clearance

  • Ground Clearance 35.0 in 889.0 mm

Tractive Effort

  • 521B 70500.0 lb 31978.0 kg

Power Train

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Hydraulic Packages

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Operator Station

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Boom and Stick

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Customer Support

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521B Standard Equipment


  • 24 volt electrical system
  • Two 12 volt maintenance free batteries with 950 CCA
  • 95 Amp alternator
  • IQAN programmable controls
  • MD3 monitor display screen


  • Hydraulically actuated hinged engine enclosure with warning alarm
  • Engine fan guard
  • Bottom guards
  • Isolation mounted cab and engine
  • Heavy duty radiator guard door


  • OPS/FOPS/ROPS/WCB/OR-OSHA certified cab
  • Dual joystick control
  • Reverse slope windshield
  • Air ride seat
  • Skylight - alternate escape hatch
  • Top escape hatch
  • 76.2 mm (3 in) retractable seat belt
  • DIN mount radio ready with speakers
  • Operator sound suppression to standards
  • Travel alarm
  • Cup holders (2)
  • Two 12 volt and one 24 volt power outlets
  • Front window, 32 mm (1.25 in) thick Margard
  • Positive filtered ventilation, pressurized cab with bi-level air conditioner, heater and defroster with manual control
  • Left side fresh air window with screen
  • Forced air fan
  • Washable floor mat
  • Neutral lever (lockout) for all controls


  • C9 ACERT engine meets U.S. EPA emission standards
  • Variable travel speed (3 ranges)
  • Under hood primary air filter
  • 43° C (109° F) degree ambient temperature cooling package: - Aluminum core ATAAC and side-by-side radiator and oil cooler - Removable debris screen - Swing out A/C condenser
  • Electric fuel priming pump
  • Fuel water separator


  • Track roller guards with access holes
  • Hydraulic track adjusters
  • Double flange track rollers
  • GFT80 Lohmann final drives
  • Cat 330 size undercarriage components
  • Nine (9) track rollers and two (2) carrier rollers per side
  • Welded, non-leveling carbody


  • Dedicated fixed displacement pilot pump
  • Dedicated variable displacement pumps for track and implement functions
  • 325 EX swing drive and swing motor
  • Electric hydraulic oil fill pump
  • 265 L (70 gal) hydraulic tank


  • 50% concentration extended life coolant


  • Heavy duty hood enclosure
  • Flexxaire fan
  • Vandalism protection
  • Spare hose storage area
  • Grease gun bracket and storage area
  • 856 L (226 gal) fuel tank

521B Optional Equipment


  • Harvester Long
  • Omission - Linkage


  • Harvester


  • 610 mm (24 in) SG pads, clipped corners, with mud/snow reliefs
  • 711 mm (28 in) SG pads, clipped corners, with mud/snow reliefs
  • 711 mm (28 in) DG pads, clipped corners, with mud/snow reliefs
  • 914 mm (36 in) Tri-track, clipped corners, with mud/snow reliefs
  • Star Carrier Rollers
  • Standard Carrier Rollers


  • Lighting Gp-HID, replaces certain standard lights
  • Heavy Counterweight
  • Starting Aid, Cold Weather - includes two additional batteries
  • Starting Aid, Arctic - includes engine and hydraulic oil Arctic heater


  • Skylight, peaked, removable

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