Description
Overview:
This bare oversize piston is a Genuine JAP component for JAP Model 34 engines (OEM 20930/020). Made from high-quality aluminium alloy, it is designed to restore correct compression and smooth running after a cylinder rebore. The "020" size denotes +0.020 inch oversize, which is approximately +0.51 mm, so it must be paired with a bore machined to the matching oversize. Supplied as a bare piston only, it does not include piston rings, gudgeon pin, or circlips. Suitable for vintage single-cylinder petrol engines commonly found in compact construction and horticultural machinery, the part helps return reliable starting and performance. This is unused old stock and may show light tarnishing, dust, or minor storage marks that do not affect its intended function.
Key Features:
- Genuine JAP part for assured compatibility and fit - OEM 20930/020
- +0.020 inch oversize (approx. +0.51 mm) for correctly rebored cylinders
- Bare piston only (no rings, gudgeon pin, or clips included)
- Aluminium alloy construction for low weight and good heat dissipation
- Helps restore compression, power, and efficiency in rebuilt engines
- Manufactured to original specifications for reliable operation when installed to the workshop manual clearances
- Suitable for heritage repairs where authentic components are preferred
- Unused old stock: expect superficial storage marks without affecting serviceability
Typical Applications:
Used during engine overhauls and rebores on JAP Model 34 units fitted to small plant and garden machinery. Typical equipment includes older cement mixers, pumps, generators, cultivators, and similar machines where a precise oversize piston is required to match a re-machined cylinder and restore dependable performance.
Also known as:
20 thou oversize piston (+0.020 in / +0.51 mm), OS piston for rebore, piston body only, bare piston (no rings), replacement piston for JAP 34, JAP 34 oversize piston, JAP OEM 20930/020 piston.
Product Specifications
| L&S Part No. | 20930/020 |
|---|---|
| Part Type | Genuine Part |
| Manufacturer | JAP |
| OEM No. | 20930/020 |
| Unit of Sale | 1 |
| Key Features | - Genuine JAP part for JAP Model 34 engines - +0.020 inch oversize for rebored cylinders - Aluminium alloy for low weight and heat dissipation - Bare piston only, no rings or pins included - Suitable for vintage single-cylinder petrol engines |
| Fits Models | 34 |
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