Yamaha PW50 60cc Big Bore Cylinder Head & Piston Kit – 44mm
New aftermarket 44 mm big-bore top-end kit for Yamaha PW50 engines. The kit increases the standard 40 mm bore to 44 mm, giving a nominal 60 cc conversion while retaining the PW50's 39.2 mm stroke.
Key Details
- Product: Cylinder, head and piston big-bore top-end kit
- Nominal capacity: 60 cc
- Bore: 44 mm
- Standard bore replaced: 40 mm
- Engine type: 2-stroke
- Condition: New
- Type: Aftermarket big-bore conversion / replacement kit
Vehicle Compatibility
| Make | Model | Years | Application |
|---|---|---|---|
| Yamaha | PW50 / PeeWee 50 | 1981–2026 | 44 mm / nominal 60 cc big-bore top-end conversion |
Yamaha / Application Reference Numbers
- PW50 standard cylinder: 4J2-11311-01 / 4J21131101
- Earlier PW50 cylinder reference: 4J2-11311-00 / 4J21131100
- PW50 cylinder head: 4J2-11111-01 / 4J21111101
- Earlier cylinder-head reference: 4J2-11111-00 / 4J21111100
- Cylinder-head gasket: 517-11181-01 / 5171118101
- Cylinder base gasket: 3PT-11351-00 / 3PT1135100
- Cylinder studs: 90116-06418 / 9011606418
- Flange nuts: 95707-06500 / 9570706500
These are Yamaha application/reference numbers for the standard components that this big-bore conversion replaces or interfaces with. The supplied kit is an unbranded aftermarket 44 mm conversion kit and is not described as a Genuine Yamaha part.
Reference Specifications
| Nominal displacement | 60 cc big-bore conversion |
|---|---|
| Bore | 44.0 mm |
| Standard PW50 bore | 40.0 mm |
| PW50 stroke | 39.2 mm |
| Reference cylinder outside width | approximately 51 mm |
| Reference cylinder total height | approximately 87.5 mm |
| Reference cylinder section length | approximately 64 mm |
| Engine type | Air-cooled 2-stroke single-cylinder application |
What's Included
- 1 × 44 mm cylinder block
- 1 × cylinder head
- 1 × 44 mm piston
- 1 × piston ring set
- 1 × piston pin
- 2 × piston circlips
- 1 × small-end / needle bearing
- 1 × cylinder-head gasket
- 1 × cylinder-base gasket
- 4 × cylinder studs
- 4 × stud nuts
- 1 × spark plug
Contents are based on the supplied kit listing and matching 44 mm PW50/QT50 big-bore kit specifications.
Important Fitment Information
Confirm the original engine configuration before ordering. Yamaha's current 2026 PW50 continues to use the standard 40.0 × 39.2 mm engine dimensions, and the long-running 4J2 cylinder/head family remains the relevant base-engine reference. This is a 44 mm big-bore conversion kit, not a standard 40 mm replacement cylinder. Compare the cylinder, stud pattern, gasket shape and top-end components with the engine currently fitted.
Condition
New. Unused aftermarket replacement / upgrade engine components.
Delivery & Returns
- Free UK delivery with an estimated 2–3 working-day service
- 30-day returns, subject to the item being returned in its original condition