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The WEICHAI WP12 Flywheel Group is a precision-engineered rotating mass assembly designed to store kinetic energy and smooth power delivery for the WP12 diesel engine platform. This complete assembly includes the flywheel itself, the starter ring gear, pilot bearing, and all necessary mounting hardware. Proper flywheel function is critical for engine balance, clutch engagement, and starting system reliability. For genuine replacement parts and comprehensive engine service components, always source from verified WEICHAI Engine Parts to guarantee OEM fitment, consistent quality, and long-term reliability.
The WEICHAI WP12 Flywheel Group is a large-diameter cast iron or forged steel disc mounted to the rear of the engine crankshaft. This essential component serves multiple functions: it stores rotational kinetic energy during power strokes and releases it during non-power strokes, smoothing engine operation and reducing torsional vibrations. The flywheel also provides a friction surface for the clutch, carries the starter ring gear for engine starting, and often incorporates timing marks for engine synchronization.
The flywheel is manufactured from high-strength nodular cast iron (QT500-7) or forged steel alloy, offering excellent wear resistance and impact strength. The outer diameter is typically 430 mm, optimized for the WP12’s power output and torque characteristics. The component’s inertia is precisely calculated to ensure smooth idle operation while allowing rapid acceleration when needed. The WEICHAI WP12 Flywheel Group is dynamically balanced to G6.3 grade or better, ensuring vibration-free operation up to the engine’s maximum rated speed of 2,100 rpm.
The WEICHAI WP12 Flywheel Group is designed for the 11.596-liter inline-six WP12 engine used in heavy trucks (HOWO, SHACMAN, FOTON), construction machinery (loaders, excavators), marine propulsion, and stationary generator sets. The assembly is compatible with all WP12 variants from Euro III through Euro V emission standards, as well as China VI engines. The flywheel is bolted directly to the crankshaft flange using high-strength Class 10.9 or 12.9 bolts, with a locating dowel ensuring correct angular alignment for timing reference.
In addition to the basic flywheel casting, the complete WEICHAI WP12 Flywheel Group includes the pressed-in starter ring gear, pilot bearing (or bushing) for the transmission input shaft, and all necessary mounting fasteners. The ring gear is induction-hardened to HRC 45-52 on the tooth flanks, providing exceptional wear resistance against the starter motor pinion. Replacement flywheel groups are available as complete assemblies or as individual components (flywheel only, ring gear only, or hardware kit). Genuine assemblies include a traceable batch number and quality certification.
For marine applications, the WEICHAI WP12 Flywheel Group is supplied with an SAE-I flywheel housing interface, compatible with standard marine gearboxes and elastic couplings. For generator applications, the flywheel is configured with a SAE-II or SAE-III housing interface. The flywheel face features a precision-ground friction surface with a flatness tolerance of 0.05 mm, ensuring consistent clutch engagement and heat dissipation.
Every genuine WEICHAI WP12 Flywheel Group undergoes 100% dimensional inspection, hardness testing, and computer-aided dynamic balancing. Counterfeit flywheels often use inferior cast iron with porosity or incorrect alloy composition, leading to cracking under load, premature ring gear wear, or dynamic imbalance that destroys the rear main seal. Always source from authorized distributors to guarantee safety, reliability, and proper engine performance.
| NO. | Part NO | Description |
|---|---|---|
| 1 | 1003570122 | Flywheel Assembly (Complete, WP12/WP13) |
| 2 | 612640020006 | Flywheel Assembly (OEM Cross-Reference) |
| 3 | 612630020354 | Flywheel Assembly (WP12 Fuel Injection Engine) |
| 4 | 612630020222 | Flywheel Assembly (SHACMAN Heavy Truck) |
| 5 | 612600020208 | Starter Ring Gear (Induction-Hardened) |
| 6 | 612600020220 | Starter Ring Gear (Alternate Specification) |
| 7 | 612630020051 | Flywheel Bolt (Class 10.9, Set of 8) |
| 8 | 612630020038 | Crankshaft Pilot Bearing (for Transmission) |
| 9 | 612600010575 | Flywheel Housing (SAE-I, Marine) |
| 10 | 61500010047 | Rear Oil Seal (Crankshaft Flywheel End) |
| 11 | 61500010100 | Rear Oil Seal (High-Temperature Version) |
| 12 | 612630020053 | Flywheel Housing Gasket |
| 13 | 612600020354 | Flywheel Ring Gear (Forge Steel, Set) |
| 14 | 612600020400 | Flywheel Pilot Bushing (Bronze) |
| 15 | 1003570122/12034 | Complete Hardware Kit (Bolts + Washers + Dowels) |
Our WEICHAI WP12 Flywheel Group is manufactured from high-strength nodular cast iron (QT500-7) with tensile strength exceeding 500 MPa. The heat-treated casting process eliminates porosity and internal stresses, preventing crack propagation under high torque loads.
Every flywheel undergoes computer-aided dynamic balancing to G6.3 grade, eliminating vibration at all engine speeds. This protects the rear main oil seal and crankshaft bearings from premature wear caused by imbalance.
The starter ring gear is induction-hardened to HRC 45-52 on tooth flanks, providing exceptional wear resistance against the starter pinion. This ensures reliable cold-weather starting for the life of the engine.
Our flywheels are manufactured using original WP12 engine drawings, ensuring bolt holes align perfectly with the crankshaft flange. No reaming or modification required for installation on HOWO, SHACMAN, and FOTON trucks.
Each WEICHAI WP12 Flywheel Group includes all required fasteners (Class 10.9/12.9 bolts, washers, locating dowel) with proper grade markings. No need to source separate hardware or risk using incorrect strength bolts.
We stock complete flywheel assemblies and individual components in warehouses across Asia, Europe, and the Americas. Express shipping options minimize downtime for fleet operators.
Unlike generic aftermarket flywheels that use low-grade cast iron or incorrect alloy composition, our WEICHAI WP12 Flywheel Group is manufactured to original equipment specifications. The nodular cast iron QT500-7 material provides 40% higher fatigue strength than ordinary gray cast iron, resisting cracking under repeated clutch engagement and torque spikes. The friction surface is precision-ground to a flatness tolerance of 0.05 mm, ensuring full clutch disc contact and preventing hot spots.
Furthermore, our flywheels include a corrosion-resistant phosphate or black oxide coating, preventing rust during storage and in marine environments. The mounting flange is machined with a precise locating dowel hole that guarantees correct angular orientation relative to the crankshaft timing marks. This is critical for engines where the flywheel carries top-dead-center (TDC) reference markings for fuel injection timing adjustment.
Technical documentation included with the WEICHAI WP12 Flywheel Group provides correct bolt torque specifications (M12 bolts: 80-100 Nm + 90° angle, Class 12.9 bolts: 120 Nm), bolt tightening sequence (cross-pattern in 3 stages), and pilot bearing installation instructions. We also include a troubleshooting guide for common issues such as clutch chatter (warped friction surface) and starter grinding (worn ring gear teeth).
For large fleet customers, we offer sample evaluation: order one WEICHAI WP12 Flywheel Group for trial installation. After validation, volume pricing applies. Many return customers report that our flywheels exceed the original service life, with over 800,000 km of reliable operation, compared to low-cost alternatives that often crack or warp within 300,000 km.
Beyond the checklist above, pay attention to any clutch engagement issues. A juddering or chattering clutch often indicates a warped flywheel friction surface. A clutch that drags (difficult to shift into gear) may indicate a worn pilot bearing or incorrect flywheel-to-clutch alignment. Addressing these issues early prevents secondary damage to the transmission and clutch assembly.
For engines operating in severe service (construction equipment, mining trucks, frequent stop-start driving), consider more frequent flywheel inspections every 150,000 km. The constant clutch engagement cycles accelerate friction surface wear and heat checking. For marine applications, inspect the flywheel for corrosion annually, as saltwater exposure can attack the cast iron surface even with protective coatings.
When resurfacing a flywheel, never remove more than 0.5 mm of material from the friction surface. Removing excessive material reduces flywheel mass, affecting engine idle stability, and may cause the clutch release mechanism to run out of adjustment range. After resurfacing, the flywheel must be rebalanced to G6.3 grade. Most professional workshops will refuse to resurface a flywheel that has already been resurfaced once, as the risk of cracking increases.
Finally, maintain a service log for the WEICHAI WP12 Flywheel Group recording installation dates, bolt torque values, ring gear condition, and any resurfacing operations. This data helps predict when components are approaching end of life. For fleet operators, standardized replacement of ring gears every 400,000 km and complete flywheel assemblies every 800,000 km eliminates starter engagement failures and clutch-related breakdowns.
In summary, the WEICHAI WP12 Flywheel Group is an essential component for any WP12 engine’s powertrain system. Its high-strength nodular cast iron construction, precision-balanced design, and induction-hardened ring gear ensure reliable performance over hundreds of thousands of kilometers. Whether you are performing a clutch replacement on a HOWO dump truck, maintaining a fleet of SHACMAN tractors, or servicing a WP12 marine propulsion engine, using a genuine flywheel assembly ensures that the engine’s rotating mass is correctly balanced and the clutch interface is properly prepared.
For workshops performing clutch or transmission work, we recommend ordering the WEICHAI WP12 Flywheel Group together with a new clutch kit, pilot bearing, and rear main seal. The flywheel is the foundation of the clutch system; renewing it along with the friction components ensures that the rebuilt drivetrain performs like new. We provide installation guides with torque specifications, runout measurement procedures, and ring gear replacement instructions for all WP12 engine variants.
Our inventory includes both standard flywheels for manual transmissions and specialized versions for automatic transmissions and marine applications. For generator sets where no clutch is present, we offer flywheels without friction surface machining (raw casting) at a reduced cost. Specify your transmission type and application when ordering to receive the correct configuration.
We also provide after-sales documentation including material certificates, CMM inspection reports, and dynamic balance certificates upon request. Every WEICHAI WP12 Flywheel Group is packaged in a foam-lined box to prevent surface damage during transit. Bulk orders receive custom export crating and documentation.
All specifications are based on original WEICHAI WP12 engine data. Actual product dimensions may vary by sub-model (Euro III, Euro V, marine, construction, etc.). Always verify part numbers against your engine’s serial number plate before ordering.
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