Yamada 771945 Pilot Valve Seat for NDP-20, NDP-25
The Yamada 771945 is a genuine Yamada pilot valve seat, used in NDP-20, NDP-25 series air-operated double diaphragm (AODD) pumps. It seals the small pilot valve that senses stroke end and signals the main air valve to shift. A worn pilot valve seat is a common cause of a pump that hesitates, stalls, or will not reverse stroke cleanly.
Genuine Yamada replacement parts are machined and molded to the original factory tolerances, so fit, alignment and seal engagement match the component being replaced. One or two per pump. Always compare the exact part number against your pump's nameplate before ordering, since Yamada varies internal components by both pump size and body material / elastomer combination.
Key Features
- Genuine Yamada replacement pilot valve seat
- Fits NDP-20, NDP-25 series AODD pumps
- One or two per pump
- Molded or machined to factory tolerances for correct fit and seal engagement
Applications
- NDP-20, NDP-25 series AODD pump service and rebuilds
- Scheduled preventive maintenance
- Restoring lost flow, leaks, or erratic cycling
- Marine, industrial, chemical and wash-down service
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 771945
- Part Type: Pilot Valve Seat
- Fits: NDP-20, NDP-25 Series
- Condition: New
Frequently Asked Questions
Q: Should I replace just this one part or the matching set?
Replace the matching set (both check balls, both diaphragms, or all the seats/gaskets disturbed in the rebuild) at the same time. Parts that run the same duty cycle wear together, and replacing only the failed one is the most common reason a rebuild needs redoing soon after.
Q: What is the earliest sign this part is wearing out?
Reduced flow, slower cycling, or - for diaphragms and check valve components specifically - fluid appearing at the air exhaust muffler, which signals a breach between the wet side and the air side.
Q: What causes this kind of wear part to fail?
Flex fatigue from normal cycling, chemical attack from the pumped fluid, or heat and hardening over time. Whichever it is, the fix is the same: replace it, and note which failure mode it was so the replacement material can be matched to the service.
Q: How do I know which elastomer is right for my fluid?
Match it to what is already on the pump nameplate or the failed part you are replacing, and check chemical compatibility against the fluid being pumped. Buna-N suits oils and fuels, EPDM suits water and many chemicals, Viton and PTFE suit aggressive or high-temperature service, and Santoprene and Hytrel give long flex life on general duty.
Not sure this is the right part? Send us a picture of your Pump Plate to https://www.clrmarine.com/Contact-Us and the CLR Marine team will confirm the correct pilot valve seat.
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