The Ametek Lamb 116764 is a three-stage, 5.7-inch quiet-bypass motor with peripheral discharge on 120 volts, and it is the high-lift member of the quiet-bypass family. Three fan stages give it a published 119.6 inches of sealed vacuum while still moving 100 CFM, which is the combination central vacuum installers and car wash operators want when the hose run is long but the motor still has to be tolerable to stand near.
Built for
- Central vacuum power units serving long tubing runs
- Self-serve car wash vacuum stations needing high lift at moderate noise
- Commercial wet and dry recovery machines on 120-volt service
- Extractors and machines with restrictive tools or long hoses
- Replacement stock for 5.7-inch three-stage quiet bypass motors
How this motor works
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.
A bypass motor carries a separate cooling fan, so the air that cools the armature and field never mixes with the air being pulled through the machine. That separation is the whole reason bypass motors are specified for wet recovery work such as carpet extraction and autoscrubber recovery, where the airstream is carrying water, foam and cleaning solution. It also means the motor is not being cooled by whatever the operator happens to be picking up.
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.
Overall height is where this one catches people out. At 7.75 inches with a 3.5-inch bolt height, a three-stage motor is meaningfully taller than the two-stage motor of the same diameter, and a power unit canister that happily took a two-stage motor may not close over this one. Measure the available height before ordering, not after.
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.
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: 5.7 in
- Stages: 3
- Airflow system: bypass, quiet bypass (QBP) build
- Air discharge: peripheral
- Voltage: 120 V
- Amperage: 10.7 A
- Maximum air watts: 382
- Sealed vacuum (water lift): 119.6 in
- Maximum airflow: 100 CFM
- Overall height: 7.75 in
- Bolt height: 3.5 in
Fitment
Ametek publishes this base number in suffix variants, and distributor cross-references to equipment makers, such as the Tennant and Windsor numbers listed against the -13 suffix, belong to that suffix rather than to the base number. No manufacturer machine compatibility list is published for the base number and none is claimed here. Match the complete part number, frame diameter, stage count, discharge style, voltage and overall height against the motor you are removing.
Frequently asked questions
How much taller is a three-stage motor than a two-stage?
Enough to matter. This one is 7.75 inches overall with a 3.5-inch bolt height. Check the clearance inside your power unit or machine housing before ordering.
What sealed lift does it produce?
119.6 inches of water lift with 100 CFM of airflow and 382 maximum air watts at 120 volts.
Is this the same as 116765?
No. Both are three-stage 5.7-inch bypass motors on 120 volts, but 116764 uses peripheral discharge in a quiet bypass build and 116765 uses tangential discharge. The housing dictates which one fits.
Why choose three stages for a central vacuum?
Because central vacuum tubing runs are long and restrictive. Three stages hold vacuum against that restriction where a two-stage motor would fall off.
What is the usual reason one of these fails?
Worn carbon brushes, which are a serviceable wear part and show up as sparking or intermittent suction. A burning smell means the armature has overheated and the motor needs replacing.
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.
