Published 2026-09-18 · Yuchai engine parts · EPID
A Yuchai YC4D overhaul kit groups every wear part of one engine rebuild into a single order. This guide explains what belongs in the kit, how an inframe kit differs, when a rebuild is justified, and what to measure before you order.
What belongs in a YC4D overhaul kit
| Group | Components | In inframe kit | In overhaul kit |
|---|---|---|---|
| Cylinder unit | Liners, pistons, rings, pins, retainers | Yes | Yes |
| Rod bearings | Connecting rod bearing shells | Yes | Yes |
| Main bearings | Main shells and thrust washers | No | Yes |
| Gaskets and seals | Full gasket set including head gasket, oil seals, O-rings | Yes | Yes |
| Valve train | Valves, guides, springs, seats where applicable | No | Yes |
| Camshaft bearings | Cam bushings | No | Yes |
Inframe kit or full overhaul?
The decision turns on the crankshaft and the oil system. If oil pressure is still within specification when hot and the journals are sound, an inframe kit - cylinder unit, rod bearings and gaskets, fitted with the engine in the chassis - is usually the economical choice. If oil pressure is low, if a bearing has failed, or if metal has circulated in the oil, the engine comes out for a full overhaul with main and camshaft bearings.
When a YC4D rebuild is justified
- Blow-by at the breather and oil consumption rising together
- Compression spread across cylinders beyond the service limit
- Oil pressure below specification at operating temperature
- Coolant loss from liner seals or cavitation pitting
- Planned maintenance on a high-hour engine before a busy season
Measurements to take before ordering
- Liner protrusion above the block deck - it decides head gasket life.
- Bore wear at three heights and two axes, to confirm standard or oversize pistons.
- Journal diameters and ovality on the crankshaft, to select bearing sizes.
- Valve recession and guide clearance if the head is part of the rebuild.
- Camshaft lobe lift on high-hour engines.
Send us these numbers with the engine serial number and we will assemble the kit with the correct sizes and quote it line by line.
Yuchai overhaul kits and cylinder unit parts
| Part number | Part | Model | |
|---|---|---|---|
| ENGINE-REPAIR-KIT | Yuchai Engine Repair Kit | engine overhaul kit | Details |
| YC4F-SERIES-ENGINE | Yuchai YC4F Series Engine Parts | YC4F | Details |
| YUCHAI-ENGINE-YC4F90-21-YC4F90-23-REBUILD-KIT-PISTON-RING | Yuchai YC4F90-21 / YC4F90-23 Rebuild Kit (Piston & Ring) | YC4F90-21 | Details |
| YUCHAI-REPAIR-KIT | Yuchai Repair Kit | engine overhaul kit | Details |
| YUCHAI-REPAIR-KIT-LINER-KIT-PISTON-KIT-YC6108G-340-9000200B | Yuchai YC6108G Repair Kit - Liner Kit & Piston Kit 340-9000200B | YC6108G | Details |
| YUCHAI-YC4D-ENGINE | Yuchai YC4D Engine Parts | YC4D | Details |
Related pages
- Diesel engine overhaul kit guide
- Inframe kit vs overhaul kit
- Yuchai overhaul kits
- Yuchai part numbers
- HS codes for engine parts