Caterpillarasphalt paver

Caterpillar BB-621C

Maintenance schedule, common problems & OEM parts breakdown

The Caterpillar BB-621C is a compact tracked asphalt paver in Cat's small-paver class, catalogued internally as the "1.4M Small Track Paver," built for narrow-mat work (driveways, parking lots, bike paths, utility patching) too tight for a full-size paver. Two distinct factory generations share the model name and chassis lineage. The earlier generation, badged BB621C under Bitelli before Caterpillar's acquisition of Bitelli around 2000, ran a 2-cylinder Hatz 2M41L mechanical diesel rated around 26 kW (35 hp) with no electronic controls. The later, Caterpillar-branded production run, carrying its own B3Y-prefix serial range, is factory-fitted with Cat's own C2.2 diesel, a 4-cylinder, 2.2 L, EU Stage IIIb engine rated around 34 kW (46 hp) with electronic fuel control. Operating weight with screed runs around 4,000 kg (8,800 lb), with the tractor alone (screed removed) around 3,300 kg (7,275 lb), riding on a diesel-hydrostatic tracked undercarriage. The hydraulically extending screed covers a base width of 1.4-2.6 m (4.6-8.5 ft), with bolt-on end extensions bringing maximum paving width to roughly 3.0 m (9.8-10 ft); there is no quick-coupler scheme, screed and extension hardware bolt directly to the machine and screed frame.

The real generational change on this model is the engine swap, not the chassis. Moving from the mechanically governed 2-cylinder Hatz to Cat's own ECM-controlled C2.2 4-cylinder brought electronic fuel control and emissions aftertreatment to a machine that previously ran with no electronics at all, and with it came fault-code diagnostics through Cat Electronic Technician that the older build simply cannot support. The compact screed, hydrostatic drive layout, and tracked undercarriage carried over largely unchanged across both generations. In today's used and parts market, the BB-621C fills a niche for contractors needing a narrow-mat tracked paver for residential and municipal work, and its value hinges on undercarriage condition (track pads, rollers, tensioning cylinders), screed plate flatness, and heating-element condition zone by zone. Because the two engine generations share nothing in common, confirming which one is actually fitted, from the serial prefix and data plate rather than just the model name, is the first step before sourcing parts, fluids, or diagnostic help.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.

Caterpillar BB-621C specifications

Engine

Engine (Cat-branded production, ~2008-up, 1.4M Small Track Paver class)	Cat C2.2 diesel, 4-cylinder
Displacement	2.2 L (135 cu in)
Bore x stroke	84 x 100 mm (3.3 x 3.9 in)
Gross power	Not published for this specific paver rating. The C2.2 industrial family spans roughly 31-49.3 bkW (41.6-66.1 bhp) across ratings; exact BB-621C output varies by configuration - verify with dealer or data plate
Emissions tier	Era-appropriate for this production run; C2.2 family covers EU Stage IIIA through Stage V / EPA Tier 4 Final depending on build date. Confirm actual tier from the machine's data plate
Earlier engine note (predecessor Bitelli-badged edition of this paver)	Hatz 2M41L, 2-cylinder diesel, gross power 26.4 kW (35.4 hp). This applies to the earlier Bitelli-branded run of the same chassis, before the Cat C2.2 repower documented in Caterpillar's own parts catalog for this model

Weights

Operating weight, with screed	4,000 kg (8,818 lb)
Tractor weight, without screed	3,300 kg (7,275 lb)
Ground pressure	0.68 kg/cm2

Dimensions

Transport length, with screed	4.05 m (13.3 ft)
Transport width	1.40 m (4.6 ft)
Transport height	2.62 m (8.6 ft)
Track (ground) contact length	1.43 m (4.7 ft)
Width with hopper open	2.80 m (9.2 ft)
Screed width, hydraulic extension range	1.4-2.6 m (4.6-8.5 ft), extendable to 3.0 m (9.8 ft) max
Maximum paving width	3.02 m (9.9 ft)
Minimum paving width	0.52 m (1.7 ft)

Performance

Maximum travel speed	4.18 km/h (2.6 mph)
Maximum paving speed	33 m/min (108 ft/min)
Gradeability	Not published in available sources

Service capacities (summary)

Fuel tank	69.3 L (18.3 gal)
Hydraulic system	73.1 L (19.3 gal)
Cooling system	22.3 L (5.9 gal)
Engine oil	Not published in available sources - verify with dealer or Cat C2.2 service manual

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

BB-621C fluids & capacities

System	Capacity	Recommended fluid
Engine crankcase (Cat C2.2, with filter)	approx. 10.6 L (2.8 US gal) per the Cat C2.2 industrial engine's generic lube-system refill spec; the exact as-installed sump volume for the BB-621C chassis (B3Y-prefix serial range) is not separately confirmed in public literature — verify against the dealer OMM for your serial range	Cat DEO (Diesel Engine Oil), SAE 15W-40 for temperate ambient temperatures; step down to Cat DEO 10W-30 or a Cat DEO-ULS low-ash grade in cold climates below roughly -18 C (0 F), per Cat's standard engine-oil viscosity-by-temperature guidance
Cooling system	approx. 22.3 L (5.9 US gal) — this figure is documented for the earlier Hatz-engine generation of this paver line; it is not independently confirmed for the current Cat C2.2/B3Y-prefix version, so treat it as approximate and verify against the OMM for your serial range (varies by configuration/series)	Cat ELC (Extended Life Coolant), factory premix; Cat DEAC (Diesel Engine Antifreeze/Coolant) is an acceptable alternate per Cat's machine fluids recommendations
Fuel tank	approx. 69.3 L (18.3 US gal) — same generation caveat as the cooling system figure above; varies by configuration/series, confirm against the current OMM	Ultra-low-sulfur No. 2-D diesel fuel; blend with No. 1-D or use a winter-grade blend in cold weather per Cat's fuel recommendations
Hydraulic system and tank	approx. 73.1 L (19.3 US gal) total system — same generation caveat as above; verify against the OMM for the C2.2/B3Y-prefix version before servicing	Cat HYDO Advanced hydraulic oil (or Cat TDTO where the OMM specifies a tractor-hydraulic-type fluid); grade by ambient temperature per Cat's hydraulic-oil viscosity chart, lighter grade in cold climates
Propel / track drive	not applicable as a separate fluid compartment — this class of small track paver runs a hydrostatic propel circuit fed from the main hydraulic system; no separate transmission or final-drive oil sump is documented for this model	n/a — covered under the hydraulic system fluid above
Grease (chassis, track-tension, screed pivot points)	serviced by grease-point interval, not a bulk refill volume	Cat Ultra 5 Moly Grease (NLGI 2) for general chassis and pivot points; Cat Advanced 3Moly Grease is an acceptable alternate per Cat's machine fluids recommendations guide

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Caterpillar BB-621C maintenance schedule

Service interval	Tasks
Every 50 h	Check engine oil level on the Cat C2.2 and look for leaks around the crankcase, oil cooler, and turbo/exhaust lines before startup. Check the hydraulic reservoir level (73 L/19.3 gal system) and inspect hoses and cylinder rod seals for weeping. Drain the fuel/water separator bowl and check for trapped condensation, especially after the machine has sat idle. Inspect track pad condition and tension via the grease-cylinder tensioning shock absorbers; watch for chunking or rubber separating from the steel core. Run the screed heating elements through a full warm-up cycle and confirm every zone comes up to temperature evenly before paving. Clean asphalt buildup off the auger, conveyor chains, and hydraulic oil cooler fins.
Every 250 h	Change engine oil and filter on the C2.2 using a Cat DEO-spec oil at the correct viscosity for ambient temperature. Replace the fuel filter/water separator element. Check the air filter restriction indicator and replace the primary element if it has tripped. Grease all screed pivot points, extension slides, and the tamper/vibrator shaft bushings. Inspect drive belt tension and clean/inspect charging-system and battery connections for corrosion. Check track roller and bogie play and re-tension if the machine has been drifting to one side.
Every 500 h	Replace the hydraulic system filter(s). Pull a hydraulic oil sample from the 73 L reservoir for lab analysis. Inspect the hydrostatic propel pump and drive motor for external leaks and sluggish response at low idle/creep speed. Clean and dielectric-grease screed height and slope sensor connectors to rule out corrosion-driven false faults. Inspect conveyor chain and auger flight wear, since speed mismatch here is the usual cause of material segregation at the screed. Check coolant level and condition and clean the radiator core of packed asphalt dust.
Every 1,000 h	Change the hydraulic oil (73 L system) with the specified Cat HYDO or TDTO-type fluid. Replace hydrostatic drive circuit filters. Check and adjust engine valve lash on the C2.2 per its factory schedule. Inspect track pads, rollers, idlers, and pins for wear beyond spec — worn undercarriage affects steering control on this machine. Load-test the battery and charging system output and inspect ground straps, a common source of intermittent no-crank complaints. Inspect screed plate flatness and check heating-element continuity zone by zone.
Every 2,000 h	Replace engine coolant with Cat ELC and pressure-test the cooling system. Inspect the hydrostatic pump and propel motor internally and rebuild if wear or leak-down exceeds limits. Inspect the main frame, hopper wear plates, and screed extension mounting hardware for fatigue or cracking. Check tamper bar and vibrator shaft bushings for play and rebuild if worn. Perform a full undercarriage inspection: tension shock-absorber cylinders, roller bogies, and drive sprockets. Connect Cat Electronic Technician (ET) to the ECM and review fault history for any unresolved CID/FMI codes.
Every 4,000 h	Overhaul or replace the hydrostatic drive pump and propel motor as a set. Renew the undercarriage — track pads, rollers, and idlers — as a full set rather than piecemeal. Rebuild or replace screed heating elements and sensor harnesses on zones showing repeated failures. Perform a top-end inspection on the C2.2 (injectors, turbocharger if fitted) alongside the rebuild. Replace worn conveyor chains and auger flights.

Servicing the BB-621C beyond the schedule

Predictive Maintenance & Fluid Analysis

Sample the 73 L hydraulic reservoir on schedule to catch hydrostatic pump or propel-motor wear before it strands the machine mid-shift. Pair C2.2 engine oil analysis with coolant checks, since both the radiator and hydraulic cooler load up gradually with asphalt dust rather than failing suddenly. Watch the fuel/water separator for condensation after storage or long idle periods. Log track tension at every check; drift to one side shows up as a tensioning problem well before it becomes a steering complaint.

Corrective & Common Repairs

Track pad chunking and rubber separating from the steel core are the most common undercarriage repairs on this class of tracked paver, usually from curb-and-gutter creep-speed work. Screed heating complaints are almost always one failed element or lead, not the whole system; isolate before replacing. Height/slope sensor connectors corrode and throw false position faults; clean and dielectric-grease them before condemning a sensor. Segregation at the screed traces to conveyor and auger speed mismatch, not the mix; check chain and flight wear first.

Overhaul & Rebuild Points

Hydrostatic pump and propel-motor rebuilds are the major wear item on this hydrostatic-drive paver; persistent creep-speed lag or drift after basic checks points here. Full undercarriage renewal (track pads, rollers, idlers, tensioning cylinders) comes due together once wear starts affecting steering control. Screed heating elements and sensor harnesses get replaced zone by zone as they fail, not as a wholesale swap. On C2.2-engined units, budget a top-end inspection covering injectors and turbo components alongside an ECM fault-history review.

Seasonal & Environment Servicing

Confirm which engine is fitted before cold-weather prep; the Cat C2.2 takes standard cold-start aids and a winter fuel blend, while the older Hatz-powered build has no electronics to support any of that. Give the screed its full warm-up cycle in cold weather; a rushed cold screed is the most common self-inflicted mat-quality complaint on this machine. In hot, dusty conditions, clean asphalt buildup off the radiator and hydraulic cooler fins every shift, and drain the fuel/water separator after humid storage.

BB-621C common service parts

Part number	Part	Notes
220-1523	Filter As-Engine Oil	Lubrication service	Check fitment →

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BB-621C fault codes & troubleshooting

Code	Meaning	Likely cause	What to do
CID 0100 FMI 01	Engine oil pressure low	Low oil level, worn oil pump, plugged filter, or a failed oil pressure sensor/wiring fault	Shut down and check oil level and condition first, then verify sensor wiring before condemning the pump
CID 0110 FMI 00	Engine coolant temperature high	Low coolant level, radiator fins clogged with asphalt dust/debris, failed thermostat, or a faulty coolant temp sensor	Check coolant level and clean the radiator core/screens before further diagnosis; verify thermostat operation
CID 0168 FMI 04	Battery/system voltage below normal	Weak or failing battery, loose or corroded battery/ground connections, or an alternator/regulator fault	Load-test the battery and measure charging voltage at idle and rated speed; inspect ground straps and connections
CID 0190 FMI 02	Engine speed/timing signal erratic or abnormal	Damaged crankshaft speed sensor, incorrect sensor air gap, or a chafed/broken harness wire	Inspect sensor mounting and air gap, then check harness continuity from sensor to ECM connector
CID 0247 FMI 09	Engine ECM to machine display data link abnormal update rate	Intermittent or corroded data link connector between the engine ECM and the operator display/instrument panel	Inspect and clean the data link connectors and check for a firm ECM ground before replacing components
Water-in-fuel warning icon	Water level detected in the fuel/water separator bowl	Condensation in the fuel tank or a saturated separator element, often worse after long idle periods or humid storage	Drain the separator bowl, check fuel quality, and replace the element if drainage does not clear the warning
Hydraulic oil temperature high warning icon	Hydraulic system temperature above normal operating range	Low hydraulic oil level, clogged oil cooler fins (common with asphalt dust buildup), or sustained high-load operation of the propel/auger/conveyor circuits	Check hydraulic oil level and clean the cooler core before checking for a relief valve or pump fault
Air filter restriction indicator	Intake air filter restriction above the allowable limit	Clogged air filter element from dust/debris typical of paving sites	Inspect and replace the air filter element and reset the restriction indicator

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

BB-621C attachments & work tools

Screed and width extensions

Base hydraulic sliding screed covers roughly 1.4-2.6 m (55-102 in). Bolt-on end extensions bring maximum paving width to about 3.0 m (10 ft). Whether the compaction system is tamper-bar, vibratory, or combination is not documented for this exact unit; confirm from the data plate or dealer.

Engine configuration (factory variants)

Two distinct factory powerplants exist under this same model designation. Earlier production used a 2-cylinder Hatz diesel rated around 26 kW (35 hp). Later production, identified by its own serial-number prefix, was factory-fitted with Cat's own C2.2 diesel. Verify which engine is fitted from the serial/data plate before ordering engine-driven attachments or drive components.

Hydraulic system

Hydraulic reservoir capacity is reported at roughly 73 L (19.3 gal), supplying the screed extension, tamper/vibrator, and travel circuits. Hopper capacity figures conflict across available references and are not reliable; confirm with a dealer before sizing hopper-side work.

Undercarriage and travel system

Track-mounted (not wheeled), diesel-hydrostatic drive. Paving speed up to about 33 m/min (108 ft/min), travel speed up to about 2.6 mph (4.2 km/h). As a self-propelled base machine it has no carrier-style quick-coupler; screed and extension hardware bolt directly to the machine and screed frame.

Screed extension mounting hardware

Extension sections bolt to the main screed through a pivot-and-bolt joint on a heavy-duty extension frame, the standard mounting method used across this class of small Cat/Bitelli-derived paver screed. Exact extension-kit width increments are not documented for this specific model; treat any listed increment as class-typical, not confirmed factory data.

Electric screed heating

Electrically heated screed plates are standard practice across this size class of Cat/Bitelli paver screed, used to bring the screed to mat temperature before paving starts. Documented at the product-line level; not confirmed on an original spec sheet for this specific unit.

Operator canopy and guarding options

Hardtop canopy, canopy work lighting, and a canopy-mounted hazard beacon are catalogued options across this small-track-paver size class, which shares electrical components with sibling small Cat pavers. Not confirmed as a listed factory option specifically for this model; verify availability with a dealer.

Grade and slope control

Not documented for this exact model in available sources. Small tracked pavers of this class commonly accept aftermarket or OEM sonic-ski and slope-sensor kits for automated grade control; confirm compatibility with a dealer before fitting one.

All BB-621C assemblies by section

Every catalogued assembly group for the Caterpillar BB-621C. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Air Inlet And Exhaust System

308-2309 Connection Gp-Exhaust

15***92	Nut	3
15***60	Nut	3
15***13	Bolt	2
15***15	Washer	2

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309-6724 Manifold Gp-Exhaust

10***51	Bolt; (M8x1.25x130-mm)	1
15***92	Nut	1
15***84	Washer	1
16***41	Bolt	3

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Basic Engine

311-9025 Camshaft Gp

15***92	Key-Woodruff	1
15***38	Bolt	2
15***80	Plate	1
15***05	Bearing	1

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309-6722 Cover Gp-Valve Mechanism

15***39	Gauze; (Crankcase Breather)	1
15***62	Bolt	3
15***40	Bolt	2
15***47	Nut	4

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309-6713 Crankshaft Gp

15***87	Plug	3
15***91	Plug	1
15***94	Dowel	2
15***95	Dowel	2

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309-6712 Cylinder Block Gp

15***88	Bolt	14
15***89	Bolt	4
18***13	Stud	2
30***62	Stud	2

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321-4061 Cylinder Head Gp

16***68	Bolt; (M10x1.5x95-mm)	2
30***74	Holder	1
30***75	Seal-O-Ring	3
32***61	Cylinder Head Group	1

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309-6715 Cylinder Head Gp

15***54	Seal	4
15***56	Pin-Cotter	8
15***57	Cap	8
15***58	Spring	8

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315-5252 Drain Gp-Engine Oil

15***05	Gear-Starter; (126-Teeth)	1
15***06	Bolt	6
31***52	Drain Group-Engine Oil	1
32***54	Flywheel Group	1

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328-3296 Drive Gp-Auxiliary

13***62	Bolt; (M10x1.5x30-mm)	6
13***01	Housing-Flywheel	1
15***75	Bolt	10
15***68	Bolt	2

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308-2291 Flywheel Gp

15***60	Nut	2
15***62	Bolt	4
15***15	Washer	1
15***73	Pin	1

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308-2290 Housing Gp-Flywheel

15***84	Washer	1
16***41	Bolt	1
23***28	Plate-Lifting	2
30***90	Housing Group-Flywheel, Name-Plate (Dutch)	1

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311-9023 Housing Gp-Front

15***33	Bolt	31
15***35	Seal-O-Ring	1
15***38	Bolt	3
15***41	Seal-O-Ring	4

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339-3017 Kit-Front Gear

15***67	Rod As-Connecting	4
15***69	Bushing	1
15***70	Bolt	2
15***71	Nut	2

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309-6725 Lifting Gp-Engine

15***12	Washer	2
21***34	Plug-Drain; (Engine Oil Pan)	1
30***25	Lifting Group-Engine	1
31***60	Valve-Drain	1

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315-7813 Mounting Gp-Fan

15***92	Key-Woodruff	1
15***80	Nut	1
31***13	Mounting Group-Fan	1
32***38	Pulley-Crankshaft	1

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317-3037 Pan Gp-Oil

15***22	Pulley-Water Pump	1
31***37	Pan Group-Oil	1

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309-6714 Piston & Rod Gp

15***87	Screw-Adjustment	8
15***90	Nut	8
15***35	Seal-O-Ring	1
15***40	Lever-Rh	4

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308-2300 Pulley Gp-Crankshaft

15***61	Bolt	2
15***88	Nut	4
15***46	Stud	4
15***48	Rod	8

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308-2294 Pulley Gp-Water Pump

15***33	Seal; (Engine Oil Filler Cap)	1
21***58	Cap-Oil Filler; (Engine)	1
28***93	Seal; (Engine Oil Fill Cap)	1
28***20	Cap-Oil Filler; (Engine)	1

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308-2306 V-Belt Gp -Water Pump

22***23	Filter As-Engine Oil	1
30***06	V-Belt Group; -Water Pump, Pipe (R1j1)	1

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293-2167 Valve Mechanism Gp

15***79	Stud-Hollow	1
29***67	Valve Mechanism Group	1

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309-6716 Valve Mechanism Gp

15***36	Washer	2
15***49	Spring	1
15***50	Collar	1
15***51	Clip	1

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Cooling System

308-2302 Connection Gp-Water

13***11	Cap; (Tamper Resistant)	1
15***92	Nut	1
15***15	Washer	2
15***83	Pin	1

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309-6721 Pump Gp-Water

15***84	Washer	1
16***41	Bolt	1
17***19	Seal-O-Ring	1
29***70	Pump As-Fuel Transfer	1

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Electrical And Starting System

308-2305 Alternator Gp-Charging

16***61	Starting Motor Group-Electric	1
30***05	Alternator Group-Charging	1

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308-2311 Glow Plug Gp

15***36	Washer	2
18***65	Plug	1
29***65	Switch-Pressure; (Engine Oil)	1
30***22	Adapter	1

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315-7817 Solenoid Gp-Shutoff

23***99	Switch-Temperature; (Engine Coolant)	1
31***17	Solenoid Group-Shutoff; -Fuel	1

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333-5930 Starting Motor Gp-Electric

33***30

Starting Motor Group-Electric; -12-Volt

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361-3491 Starting Motor Gp-Electric -12-Volt

36***91

Starting Motor Group-Electric; -12-Volt

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308-2293 Starting Motor Gp-Electric

30***93

Block, Starting Motor Group-Electric

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163-3361 Starting Motor Gp-Electric

16***61

Starting Motor Group-Electric

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315-7819 Switch Gp-Pressure -Engine Oil

31***19

Switch Group-Pressure; -Engine Oil

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308-2317 Switch Gp-Temperature -Engine Coolant

30***17

Pipe (Lg2), Switch Group-Temperature; -Engine Coolant

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Engine Arrangement

326-4001 Engine Ar-Primary

30***90	Housing Group-Flywheel, Name-Plate (Dutch)	1
30***91	Flywheel Group	1
30***93	Block, Starting Motor Group-Electric	1
30***94	Pulley Group-Water Pump, Pipe (Rlb1)	1

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Fuel System

311-9024 Governor Gp

15***35	Support-Plug	1
15***76	Nut	2
15***77	Washer	2
17***85	Glow Plug	4

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315-7814 Pump & Mtg Gp-Fuel Transfer

15***12	Washer	1
31***37	Lever-Control	1
31***14	Pump & Mtg Group-Fuel Transfer	1
32***98	Solenoid; (Fuel Shutoff)	1

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311-9026 Pump Gp-Fuel Injection

24***70	Bushing	1
24***71	Solenoid; (Starting Motor)	1
24***73	Bushing	1
24***74	Drive-Motor	1

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Lubrication System

308-2297 Filler Gp-Engine Oil

15***28	Gasket-Cover; (Water Temperature Regulator)	1
16***01	Bolt	2
29***96	Cover-Housing	1
30***97	Filler Group-Engine Oil	1

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308-2298 Filter Gp-Engine Oil

15***60	Nut	3
15***61	Bolt	4
15***17	Plug	1
15***31	Plug	2

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308-4735 Mounting Gp-Engine Oil Filter

15***20	Gasket	2
16***01	Bolt	8
19***29	Flange	2
30***35	Mounting Group-Engine Oil Filter	1

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309-6717 Pump Gp-Engine Oil

15***92	Nut	2
15***26	Manifold-Exhaust	1
15***27	Gasket-Exhaust	1
15***28	Bolt	6

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Machine Arrangement

331-9371 Common Ar

32***01	Engine Ar-Primary	1
33***71	Common Ar	1

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BB-621C serial number reference

The PIN plate sits on the paver's main frame near the tractor/engine compartment, usually on the right-hand side rail below the operator platform or on the frame cross-member near the engine bay; some units also carry a duplicate plate inside the engine cover. Read the first 3 characters as the model/manufacturing prefix (e.g. B3Y), followed by a sequential unit number; newer full-length PIN plates show a longer CAT-format code where the prefix is embedded further into the string, so match the whole plate against your service manual's serial-number-index page rather than assuming a 3-character read.

Prefix	Identifies	Notes
B3Y	1.4M small track paver, Cat C2.2 diesel engine	Parts-catalog machine range B3Y00001-up. This is the Caterpillar-branded BB-621C build (post Bitelli-to-Cat Paving Products transition), fitted with the Cat C2.2. Confirm exact model year against your unit's PIN plate with your dealer.

Frequently asked questions

What engine does the Caterpillar BB-621C use?

It depends on which generation you have. Cat-branded production, carrying a B3Y-prefix serial range and marketed as the 1.4M Small Track Paver, runs Cat's own C2.2, a 4-cylinder, 2.2 L diesel rated around 34 kW (46 hp), EU Stage IIIb, with electronic fuel control. Earlier Bitelli-badged units, built before Caterpillar's acquisition of Bitelli, ran a 2-cylinder Hatz 2M41L mechanical diesel rated around 26 kW (35 hp) with no electronics. Confirm which engine is actually fitted from the serial prefix and data plate before ordering parts or fluids, since the two have nothing in common.

What is the operating weight of the BB-621C?

Operating weight with screed is around 4,000 kg (8,800 lb); the tractor alone, without screed, is around 3,300 kg (7,275 lb). These figures come from documentation for this compact tracked-paver chassis family; treat them as approximate and confirm against the OMM for your exact serial range, since weight shifts with screed width and options fitted.

What replaced the Caterpillar BB-621C?

No source confirms one specific, clearly documented successor. Caterpillar's small tracked-paver lineup continued in this size class under related model naming after the BB-621C, but nothing publicly ties a single model to it as a direct factory replacement. Check with your Cat dealer for the current equivalent in Caterpillar's compact/small track paver lineup.

What BB-621C owners discuss

What do operators say about the BB-621C's tracked propulsion and hydraulics?

The BB-621C is a hydrostatic tracked machine; the engine drives all hydraulic functions (propel, conveyors, augers, screed lift) off a common pump group. Crews report the system handles fine at paving speed, but low-idle creep-speed control is where sluggish response shows up if hydraulic oil is cold or filters are past due, so warm the system before fine-grade work. Track drift to one side usually traces to uneven track tension rather than a pump fault. Persistent drift or loss of propel power after basic checks should go to a dealer for pump/motor diagnosis.

What undercarriage wear pattern is typical for this size of tracked paver?

Like other compact tracked pavers, the rubber-bonded track pads and rollers wear fastest from curb-and-gutter creep-speed work and from paving over hot, abrasive mix that packs under the frame. Watch for chunking or separation of rubber from the steel core on the pads, and check roller/bogie play at every tension check. Track tension on this class of paver is held by grease-cylinder shock absorbers; running tracks too tight accelerates bushing and pin wear just as much as running them too loose. Track and roller wear beyond spec affects steering control, so have your dealer verify tension and wear limits.

Does the BB-621C's engine identity change between production runs, and does that affect what quirks to expect?

Yes, and it matters for diagnosis. Machines carrying the Cat serial prefix (B3Y-prefix, marketed as the 1.4M Small Track Paver) run the Cat C2.2, a Stage IIIb diesel rated around 34 kW (46 hp) with electronic fuel control and an ECM. Earlier machines badged BB621C under Bitelli, before the Cat rebadge, ran a completely different engine, a 2-cylinder Hatz 2M41L, mechanically governed with no electronics. Fault-code and injector troubleshooting for the Cat C2.2 does not carry over to the older Hatz-powered unit, and vice versa. Confirm which engine is actually fitted before chasing a code or ordering parts.

What electrical or sensor faults come up most on this class of small Cat paver?

Screed height and slope sensors are the most commonly cited nuisance fault across Cat's small-to-mid track paver line; corrosion or moisture at the sensor connector throws an unexpected-position or wiring fault before the sensor itself is actually bad. Charging system and starter wiring are the next most common complaint on machines that sit outside between paving seasons, and a weak or intermittent alternator connection shows up as random low-battery or no-crank complaints that look like an ECM problem but usually aren't. Clean and dielectric-grease the connectors first. If fault codes persist, have your dealer verify the sensor and harness.

Are there known screed heating complaints on this paver?

Same complaint owners raise about small heated screeds generally: uneven heat-up across plate sections when one heating element or its temperature sensor has degraded, leaving cold spots that show up as mat texture problems right at startup. The screed heat system is designed to flag an individual failed element rather than force a wholesale heater swap, so an uneven-heat complaint is usually one element or its lead, not the whole system. Give the screed its full warm-up time before paving; rushing a cold screed is the most common self-inflicted mat-quality complaint on this size of machine.

What conveyor and auger issues are typical?

Segregation at the screed (coarse material piling to one side or the center) is most often traced to conveyor and auger speeds falling out of sync rather than a mix problem. Chain and flight wear on the conveyors, and paddle wear on the augers, are expected wear items on any paver run through abrasive mixes, and owners note it usually shows up first as inconsistent head-of-material height rather than an obvious component failure.

What should a buyer check on a used BB-621C before purchase?

Confirm which engine is actually fitted (Cat C2.2 on B3Y-prefix machines versus the older Bitelli-era Hatz 2-cylinder) since parts, fluids, and diagnostics differ completely between the two. Beyond that, run the same checklist any small tracked paver buyer should: track pad condition and tension, roller/bogie play, screed plate wear and flatness, heating-element function across every zone, conveyor chain and auger flight wear, hydraulic hose condition and cylinder leak-down, and whether the hour meter reading matches overall wear. Start the engine cold and watch for hard starting or smoke, then cycle every hydraulic function (screed lift, extension, conveyors, augers) checking for lag or noise. Given the wide age spread on used units of this model, have your dealer or a qualified paver technician verify undercarriage and hydraulic pump/motor condition before final purchase.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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