Matched Set Shipped — connecting rod bolts paired with verified bearing grades and gaskets for a complete D722 bottom-end refresh.
Technical Specifications
| Parameter |
Value |
| Part Number |
16851-22140 |
| Product Type |
Connecting Rod Bolt |
| Cross-Reference |
1685122140, 16851-2214-0 (reference only) |
| Machine Fitment |
B7300HSD, B7400HSD, BX1870, BX2370, KX41-3, U17, RTV900, ZD321 (compatible with Kubota equipment) |
| Engine Fitment |
D722 |
| Material |
SCM435 High-Tensile Alloy Steel, Heat-Treated |
| Tensile Strength |
1,200 MPa minimum |
| Surface Hardness |
HRC 37–41 |
| Thread Type |
Rolled Threads |
| Surface Treatment |
Black Oxide Finish |
| Standards |
ISO 9001, ISO 898-1 Class 10.9 |
| Condition |
New Aftermarket |
Application Suitability
| Engine System |
Related Components |
| Bottom-End Assembly |
Connecting Rod Bearings (STD / 0.25 / 0.50 oversize), Crankshaft Main Bearings |
| Lubrication & Cooling |
Oil Pump, Thermostat, Overhaul Gasket Kit |
| Cylinder Components |
Pistons, Piston Rings, Cylinder Liners (if bore requires honing) |
Why a New Bolt Is Not Enough to Prevent Repeat Failure
Replacing this fastener without verifying the connecting rod geometry or bearing clearance often leads to a second teardown within a few hundred hours.
A rod bolt installed into a distorted big-end bore fails to achieve the required clamping load, regardless of its tensile rating. In our experience sourcing components for rebuild shops across Central Asia and European distributors, the root cause of repeated connecting rod bolt engine rebuild failures is rarely the bolt itself. It is usually a systemic issue: a crankshaft reground to an oversize dimension without updating the bearing shells, or a connecting rod that has stretched beyond its service limit during a previous seizure event. [NEED_CITE: diesel engine connecting rod big-end bore out-of-round tolerance limits]
The Position of the Fastener in the D722 Powertrain
This connecting rod bolt belongs to the D722 engine's bottom-end assembly, where matched fastener clamping load is critical during rebuilds. The D722 is a compact, liquid-cooled diesel engine widely used in agricultural tractors, compact excavators like the KX41-3, and commercial mowers. The cyclic loading on these bolts is immense. When planning an overhaul, this fastener must be treated as a stretch-to-yield component that is replaced as a complete set alongside the connecting rod bearings and the crankshaft main bearings.
Matching Dimensions to the Rebuild History
Engines that have been in service for extended periods rarely remain at standard factory dimensions. If the D722 crankshaft has been reground due to scoring, the standard connecting rod bearings will have excessive clearance, leading to low oil pressure and a knocking sound that eventually destroys the new bolt. Before dispatching the connecting rod bolt engine rebuild kit, we verify the crankshaft journal diameter and match the bearing grade—available in STD, 0.25 and 0.50 oversize—to the actual machined dimensions of the rotating assembly. [NEED_CITE: engine bearing shell clearance grades and crankshaft regrind standards]
Material and Thread Integrity Under Thermal Cycling
The SCM435 alloy steel construction and heat treatment to HRC 37–41 provide the necessary fatigue resistance for the D722's combustion pressures. The rolled thread profile is superior to cut threads because it compresses the grain structure rather than cutting across it, improving resistance to crack propagation at the thread root. Furthermore, the black oxide finish is not merely for corrosion resistance; it acts as a mild lubricant during torquing, ensuring the friction coefficient remains stable so that the applied torque translates accurately into the required bolt stretch.
The Hidden Cost of Ignoring the System
Sourcing only the failed hardware without addressing the lubrication fault or the big-end bore distortion results in predictable callbacks. A repair shop that installs new bolts into a connecting rod with a tapered bore will see the bolt loosen as the engine reaches operating temperature. This leads to spun bearings, scored crankshaft journals, and in severe cases, a rod exiting the block. The cost of a single missed diagnostic step multiplies the labor hours and parts consumption required to make the machine operational again. [NEED_CITE: root cause analysis of diesel engine bearing and fastener failures]
Sourcing the Complete Bottom-End Solution
Our production and sourcing lines cover both self-produced and qualified partner supply under one warranty account. We provide the connecting rod bolt engine rebuild components alongside the matching bearing shells and overhaul gasket kits, ensuring all dimensions are compatible with the specific D722 variant. Technical support is available to confirm the exact bearing grade required based on your crankshaft measurements, and sample supply is offered for fitment confirmation before bulk commitment on fleet overhauls.
Documentation & Verification
- Commercial invoice listing part number 16851-22140 and matched bearing grades.
- Cross-reference sheet confirming interchange compatibility for identification purposes.
- Quality inspection record verifying shank diameter tolerance of ±0.02 mm.
- Packing photographs showing blister packs and reinforced cardboard boxes.
- Warranty terms covering manufacturing defects for the specified period.
Installation & Rebuild Sequence
- Inspect connecting rod big-end bore for out-of-round and taper before installing new bolts.
- Lubricate bolt threads and under-head radius with engine oil prior to assembly.
- Tighten in two stages to the specified torque, then verify the angle of rotation.
- Check side clearance and end-play after assembly to ensure no binding occurs.
Preparing Your Rebuild Inquiry
To ensure the connecting rod bolt engine rebuild package arrives ready for the bench, provide the D722 engine serial number and the measured crankshaft journal dimensions. If the engine has undergone previous overhauls, note the last installed bearing grade so we can match the oversize requirements accurately.
Frequently Asked Questions
Q: What else should I replace when doing a D722 rod bolt job?
A: This is a system-level repair. You must replace the connecting rod bearings, check the crankshaft main bearings, and install a new overhaul gasket kit. Reusing old bearings with new bolts often masks underlying clearance issues that cause repeat failures.
Q: How do I know if my crankshaft has been reground?
A: Measure the connecting rod journal diameter with a micrometer. If it reads below the standard factory specification, you need oversize bearing shells. Installing standard bearings on a reground shaft will cause immediate low oil pressure and bolt fatigue.
Q: Are rod bolts for different D722 serial variants interchangeable?
A: While the external dimensions may appear identical, the tensile requirements and torque specifications can vary between early and late production D722 engines. We verify the engine serial number to ensure the SCM435 material grade matches the specific block casting.
Q: What is the root cause of repeated rod bolt failure?
A: It is rarely the bolt itself. Common systemic causes include a distorted connecting rod big-end bore, incorrect bearing clearance leading to impact loading, or lubrication starvation. Addressing the fault that caused the failure is essential.
Q: How do I confirm my exact D722 engine model before ordering?
A: Locate the engine serial number plate, usually on the valve cover or the block side. If the plate is worn, provide a photograph of the injection pump and the manifold layout so our technical team can cross-reference the variant.
