Yamada 711937 Pilot Valve Spring for NDP-40 to NDP-80
The Yamada 711937 is a factory pilot valve spring used in NDP-40, NDP-50 and NDP-80 Series pumps. It is a small part with a direct effect on how the pump runs, because the air motor is a timed mechanism and the spring is part of the timing.
Fit springs in pairs where the pump uses two. One relaxed spring and one new one gives different timing on each half of the cycle, which is felt as an uneven beat.
Key Features
- Genuine Yamada replacement pilot valve spring
- Fits NDP-40, NDP-50 and NDP-80 Series pumps
- Two per pump
- Provides the return force that times the air valve shift
- Restores clean, even cycling at low air pressure
- Direct replacement, no adjustment required
Applications
- NDP-40, NDP-50 and NDP-80 Series pumps
- Air valve and pilot valve overhauls
- Curing hesitation or uneven cycling
- Restoring reliable operation at low air pressure
- Service after moisture has corroded the air motor internals
- Marine, industrial and transfer duty
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 711937
- Part Type: Pilot Valve Spring
- Fits: NDP-40, NDP-50 and NDP-80 Series pumps
- Quantity Used: Two per pump
- Series Port Size: 2 in on the NDP-50 Series
- Condition: New
Frequently Asked Questions
Q: What happens if a spring breaks?
The valve loses its return and the pump usually stops mid stroke. The broken piece stays in the valve, so the assembly needs to be cleaned out as well as re-sprung.
Q: Can I stretch a tired spring to restore it?
No. Stretching changes free length without restoring rate, and the timing ends up wrong in a way that is hard to diagnose later.
Q: How can I tell a spring has relaxed?
Compare its free length against the new one side by side. A spring that is visibly shorter has lost rate, and a spring with corrosion pitting should be replaced whatever its length.
Q: The pump only runs at high air pressure. Is the spring the problem?
It is a strong candidate. A weak spring needs more pressure to complete the shift, so the pump works when pushed hard and hesitates or stalls when the air is turned down.
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 pilot valve spring.
CLRMarine
