The LiftMaster K16-51219 is a 4L420 V-belt used in select LiftMaster gate operator drive assemblies. The belt transfers power between pulleys and can affect operator speed, smoothness, and torque transfer. A belt that is glazed, cracked, stretched, oil-contaminated, or improperly tensioned can slip under load and make the operator seem weak even when the motor is still good.
The 4L420 designation generally points to a 4L section belt with approximately 42 inch outside length, but LiftMaster fitment still depends on the operator design and pulley spacing. Supplier references point primarily to SL3000 and SL3000UL slide gate operator use, with some descriptions mentioning specific heavy-duty swing gate motor assemblies requiring the same 42 inch belt. Use the original part callout to avoid ordering the wrong belt length.
| Manufacturer | LiftMaster |
|---|---|
| Product Type | V-belt |
| Part Number | K16-51219 |
| Belt Size | 4L420 |
| Approximate Belt Type | 4L fractional horsepower V-belt |
| Application | Gate operator pulley drive system |
| Known Model References | SL3000 / SL3000UL in supplier listings |
| Notes | Confirm belt length, pulley alignment, and tensioning requirements |
Mechanical drive parts usually fail because of wear, misalignment, loose hardware, poor chain or belt tension, or a worn supporting shaft/bearing. Correct the cause of wear before installing the replacement part.
Gate and barrier operators can move heavy equipment and may contain high-voltage circuits. Disconnect power according to the operator manual and use a qualified gate technician for electrical diagnosis, unsafe movement, or commercial operator service work.
K16-51219 is a LiftMaster replacement belt used in the drive or retaining assembly described on this product page. It should be matched to the operator parts diagram and original part number.
Confirm the original part number, operator model, diagram location, and physical dimensions. For drive parts, also compare chain or belt size, bore, keyway, tooth count, pulley diameter, or retaining groove as applicable.
No. Many LiftMaster mechanical service parts look similar but differ by bore, keyway, tooth count, diameter, offset, belt profile, or operator generation.
Common signs include rough movement, chain or belt slip, noise, vibration, worn teeth or grooves, loose fit on the shaft, damaged retaining hardware, or inconsistent gate travel.
Inspect the mating chain or belt, shaft, bearings, keys, set screws, guards, covers, and overall alignment. On powered gate equipment, use safe service procedures and a qualified technician when needed.