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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.

Cat Specs


Gross Power
303 HP

Operating Specifications

Maximum Reach - With Attachment
26.5 ft


Operating Weight - Without Attachment
60629 lb

Service Refill Capacities

Engine Oil
10.3 gal (US)
Cooling System
10.8 gal (US)
Fuel Capacity
226 gal (US)
Hydraulic System
118 gal (US)
Swing Drive
2.6 gal (US)


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

Hydraulic System

Pumps (4)
Dedicated variable displacement pump for saw motor - 55 cc
Pumps (2)
Dedicated variable displacement pump for travel circuit - 200 cc
Pumps (3)
Dedicated variable displacement pump for boom and implement functions - 200 cc
Pumps (1)
Electric hydraulic oil fill pump

Power Train

Engine Model
Cat® C9 ACERT™
Rated Power - 2,100 rpm
282 HP
Gross Power
303 HP
537 in³
Gross Power - 1,800 rpm
303 HP

Track Length

Track Length
191.1 in


8.5 in
330 EX (D7)

Operating Weights - Without Heads, Standard Counterweight

Track Feller Buncher - 521B
60629 lb

Boom System

Track Feller Buncher - Lift Over Front of Tracks: Bare Pin Lift at Maximum Reach - Without Head
6100 kg @ 6.2 m (13,500 lb @ 20 ft 6 in)
Track Feller Buncher - Lift Over Front of Tracks: Maximum Reach - With Head
26.5 ft

Ground Clearance

Ground Clearance
35 in

Track Gauge

102 in

Tractive Effort

70500 lb