Yamaha Piston Kit – Fits Yamaha 40HP 2-Stroke E40X/40XMH (Replaces 66T-11630-00, 66T-11631-01, 66T-11631-00)
Yamaha Piston Kit – Fits Yamaha 40HP 2-Stroke E40X/40XMH (Replaces 66T-11630-00, 66T-11631-01, 66T-11631-00) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Yamaha Piston Kit – Fits Yamaha 40HP 2-Stroke E40X/40XMH (Replaces ...
Product Details
This is an aftermarket Yamaha Piston Kit designed for Yamaha 40HP 2-Stroke twin-cylinder engines, specifically models E40X and 40XMH manufactured between 1998 and 2002. The kit contains all the essential components for a single-cylinder rebuild, including the piston, piston rings, wrist pin, and clips.
It serves as a direct replacement for Yamaha OEM part numbers 66T-11630-00, 66T-11631-01, and 66T-11631-00, ensuring proper fit and function.
- Engineered for direct-fit installation.
- Designed for 2-stroke gasoline engines.
- Complete kit for one cylinder.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 66T-11630-00 | Interchangeable Part |
| Yamaha | 66T-11631-00 | Interchangeable Part |
| Yamaha | 66T-11631-01 | Interchangeable Part |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This piston kit is compatible with specific Yamaha 40 HP models produced from 1998–2002.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 40X | 40 | 2-Stroke | 1998–2002 | 66T-11630-00, 66T-11631-01, 66T-11631-00 | |
| Yamaha | 40XMH | 40 | 2-Stroke | 1998–2002 | 66T-11630-00, 66T-11631-01, 66T-11631-00 | Manual tiller handle |
| Yamaha | 40XW | 40 | 2-Stroke | 1998–2002 | 66T-11630-00, 66T-11631-01, 66T-11631-00 | Remote control |
| Yamaha | E40X | 40 | 2-Stroke | 1998–2002 | 66T-11630-00, 66T-11631-01, 66T-11631-00 | Export model |
| Yamaha | E40XMH | 40 | 2-Stroke | 1998–2002 | 66T-11630-00, 66T-11631-01, 66T-11631-00 | Export model, manual tiller handle |
| Yamaha | E40XW | 40 | 2-Stroke | 1998–2002 | 66T-11630-00, 66T-11631-01, 66T-11631-00 | Export model, remote control |
Technical Specs
- Product Type
- Piston Kit
- Installation
- Direct Replacement
- Fuel Type
- Gasoline (Regular unleaded)
- Housing Material
- Aluminum Alloy
- Housing Color
- Silver/Metallic
- Package Dimensions
- 8.5 in × 9.3 in × 2.0 in
- Cylinder Bore
- 80.0 mm (3.15 in)
- Stroke
- 70.0 mm (2.76 in)
- Engine Displacement
- 703.0 cm³
- Engine Design
- Twin cylinder (2-cylinder)
What’s in the Box
- 1 x Piston
- 1 x Piston Ring Set
- 1 x Piston Pin
- 2 x Piston Pin Clips
Installation Notes
- Ensure the engine is off and cool. Disconnect the battery and fuel supply.
- Drain the engine oil and coolant into appropriate containers.
- Remove the cylinder head and any other components obstructing access to the piston.
- Carefully remove the old piston assembly from the connecting rod.
- Thoroughly clean the cylinder bore and inspect for damage or excessive wear.
- Install the new piston rings onto the new piston according to service manual guidelines.
- Lubricate the new piston, rings, and cylinder wall with 2-stroke engine oil.
- Install the new piston assembly, ensuring the correct orientation.
- Reassemble the engine by reversing the disassembly steps. Use a torque wrench to tighten all fasteners to OEM specifications.
- Refill engine oil and coolant, then check for leaks before starting the engine.
Troubleshooting & FAQ
How do I confirm this piston kit fits my engine?
Verify your engine's model (e.g., E40X, 40XMH) and year (1998–2002) against the "Engine & Model Compatibility" table. Cross-referencing your existing part number with those listed in the "Part Number Matrix" is the best way to ensure an exact match.
What are the signs of a worn or failing piston?
Common symptoms include a loss of compression, reduced engine power, excessive blue or white smoke from the exhaust, an audible knocking or rattling sound from the engine, and metal shavings found in the engine oil.
What is the difference between part numbers 66T-11630-00, 66T-11631-01, and 66T-11631-00?
These part numbers are considered interchangeable for the specified Yamaha models. The different numbers typically represent minor manufacturing revisions or updates over time, but they share the same critical dimensions and specifications for fit and function.
Is this kit for one or both cylinders?
This kit contains the components to service one cylinder. If you are rebuilding both cylinders of your twin-cylinder engine, you will need to purchase two kits.
What is the standard bore size for this piston?
This is a standard-size piston designed for a cylinder bore of 80.0 mm. It is not an oversized piston for bored-out cylinders.
Do I need to check ring end gap?
Yes, it is highly recommended to check the piston ring end gap with a feeler gauge before installation, as per your engine's service manual. This ensures proper sealing and performance.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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