Yamada 711931 Air Valve Body for NDP-40 to NDP-80
The Yamada 711931 is a factory air valve body used in NDP-40, NDP-50 and NDP-80 Series pumps. The air motor is what makes the pump self reciprocating: the pilot valve senses the end of the stroke, the main valve shifts, and air is redirected to the other chamber.
Whenever the air motor is opened, replace the gaskets, the seal rings and the springs while you are in there. They cost very little next to the time taken to reach them, and leaving a tired one in place is the usual reason a rebuilt pump is back on the bench a month later.
Key Features
- Genuine Yamada replacement air valve body
- Fits NDP-40, NDP-50 and NDP-80 Series pumps
- One per pump
- Part of the air distribution system that cycles the pump
- Machined to the factory specification for correct valve timing
- Direct replacement, no modification or adjustment required
Applications
- NDP-40, NDP-50 and NDP-80 Series pumps
- Air motor overhauls and rebuild work
- Curing stalling, hesitation or continuous exhaust
- Service after moisture or debris has entered the air supply
- Scheduled preventive maintenance on hard working pumps
- Marine, industrial and transfer duty
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 711931
- Part Type: Air Valve Body
- Fits: NDP-40, NDP-50 and NDP-80 Series pumps
- Quantity Used: One per pump
- Series Port Size: 2 in on the NDP-50 Series
- Condition: New
Frequently Asked Questions
Q: Why does the pump exhaust continuously without cycling?
Air is crossing between passages that should be isolated - a failed gasket, a worn seal ring or a valve face that is no longer flat.
Q: Does air pressure affect how long the air motor lasts?
Yes. Running at more pressure than the duty needs increases impact and wear throughout the motor, so set the regulator to the lowest pressure that gives the flow you need.
Q: The pump stalls at the end of a stroke. Where do I start?
Check whether there is product at the muffler. If there is, a diaphragm has split. If there is not, the fault is on the air side - a tired spring, a worn seal ring, a blown gasket or a scored valve face.
Q: What damages the air motor fastest?
Water and dirt in the compressed air supply. A filter regulator with a water trap, drained regularly, does more to extend air motor life than any other single measure.
Not sure this is the right part? Send us a Picture of the Pump Plate on your pump and the CLR Marine team will confirm the correct air valve body.
CLRMarine
