The Ametek Lamb 116551-50 is a two-stage, 4.8-inch vacuum motor with peripheral discharge and ball-and-sleeve bearings, wired for 120 volts. The 4.8-inch frame is the compact size, the one specified when a portable spotter or a small extractor has to fit a real motor into a housing that has no room to spare and still pull usable water lift. It is sold as a replacement motor for technicians and owner-operators keeping small equipment in service.
Built for
- Portable carpet spotters and compact extractors on a 4.8-inch motor housing
- Small wet and dry recovery machines where a 5.7-inch motor will not fit
- Compact commercial canister vacuums
- OEM and repair-shop replacement stock for 4.8-inch two-stage motors
- Detailing and auto-interior machines built on the compact frame
How this motor works
Peripheral discharge exhausts cooling air around the full circumference of the motor housing rather than through a single port. In a canister or power unit that has room around the motor, peripheral discharge keeps exhaust noise diffuse and simplifies the mounting, which is why it shows up so often in central vacuum power units and quiet-bypass builds.
Stage count is the trade-off that decides which motor belongs in a machine. Each additional fan stage buys sealed lift and costs airflow. A single-stage motor moves the most air and is right behind a short hose; a two-stage motor is the general-purpose choice; a three-stage motor is what you want when the hose run is long or the tool is restrictive and the machine has to hold vacuum against that restriction.
Ball-and-sleeve bearing construction is worth understanding before ordering. One end runs a ball bearing and the other a sleeve, which keeps cost and length down on a compact motor. It is a normal specification on this frame size, but it is not the same as the double-ball construction used on larger commercial motors, and a machine that calls out double ball bearings should get a double-ball motor.
Carbon brushes are the wear part on any Ametek Lamb motor, not the motor itself. Ametek's own guidance is that a set of brushes can be changed twice before the armature and the rest of the assembly need replacing, with roughly 60 percent of original life left after the first change and about 40 percent after the second. If a machine has begun surging, losing suction intermittently, or throwing sparks at the commutator, brushes are the first thing to check before condemning the motor.
The one symptom that is not a brush job is a burning smell. Technicians on carpet-cleaning and contractor forums are consistent about this: a scorched odor means the armature has overheated where the brushes ride, and the machine should be shut down at once rather than run to the end of the job. A motor that has cooked its armature is a replacement, not a repair.
The other killer is water. Extractor and wet-recovery operators point out that it is effectively impossible to never overfill a recovery tank, and that the solution being picked up often carries degreaser. Water and foam that reach the windings do damage that no brush change undoes, which is why float shut-offs and inline filters matter as much as the motor spec does.
Ametek Lamb part numbers are not interchangeable by diameter alone. Before ordering, pull the old motor and match four things: frame diameter, number of fan stages, discharge configuration and nameplate voltage. Two motors that share a body size can have completely different gasket surfaces, lead lengths and airflow paths, and a mismatch usually shows up as a motor that physically drops in but never reaches its rated suction.
Specifications
- Fan diameter: 4.8 in
- Stages: 2
- Air discharge: peripheral
- Voltage: 120 V
- Maximum air watts: 214
- Sealed vacuum (water lift): 76.5 in
- Maximum airflow: 87.7 CFM
- Speed: 19,900 RPM
- Bearings: ball and sleeve
- Construction: thermoset fan end bracket, aluminum commutator bracket
- Termination: wire leads, no plug
- Shipping weight: 4.2 lb
Fitment
A note on conflicting source data, stated rather than papered over: suppliers do not agree on how this motor's airflow system is classified. Several distributors describe 116551-50 as a bypass motor with peripheral discharge; others, including the source behind this listing's own original title, classify it as thru-flow. Bypass and thru-flow are mutually exclusive designs, and the distinction matters, because a thru-flow motor is cooled by the working airstream and a bypass motor is not. No claim is made here either way. Amp draw is also quoted differently by different sources, and no source publishes an input wattage or overall height. If your machine requires one design specifically, confirm it before ordering.
Frequently asked questions
Is 116551-50 a bypass or a thru-flow motor?
Sources disagree and we do not claim one. Some distributors list it as bypass with peripheral discharge, others as thru-flow. If your machine is built around one design specifically, confirm before ordering.
What does ball-and-sleeve bearing mean?
One end of the armature runs in a ball bearing and the other in a sleeve bearing. It is standard on compact motor frames and is not interchangeable with a double-ball specification.
Will a 5.7-inch motor fit in place of this one?
No. The 4.8-inch frame is a different physical size with a different mounting footprint. Match the frame diameter to the housing the machine was built around.
How much suction does it produce?
Published figures are 76.5 inches of sealed vacuum, 87.7 CFM of maximum airflow and 214 maximum air watts at 120 volts.
Does it come with a power cord or plug?
No. The motor terminates in wire leads with no plug, which is how replacement motors are supplied so the installer can match the machine's existing wiring.
Discount Cleaning Products is a United States based dealer for Ametek Lamb vacuum motors and stocks the matching carbon brush kits, gaskets and mounting hardware alongside them. Our team works with these motors every day across central vacuum systems, extractors, autoscrubbers and shop equipment, and can help you confirm frame size, stage count, discharge style and voltage against the motor already in your machine before you order.
