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NGK 7840 Spark Plug
| Brand | NGK 7840 |
|---|---|
| Resistance | 5000 |
| Ground Electrode Tip Design | Standard |
| Ground Configuration | Standard |
| Ground Electrode Core Material | Nickel |
| Electrical Terminal Type | Stud |
| Center Electrode Core Material | Copper |
| Center Electrode Tip Material | Nickel |
| Pre-Gap Size | .028 |
| Ground Electrode Quantity | 1 |
| Hex Size | 5/8 |
| Insulator Height | 50.00 |
| Manufacturer Heat Range | 5 |
| Seat Type | Flat |
| Reach | .5 |
| Thread Diameter | 10.00 |
| Part Number | Cr5hsa |
| Stock Number | 7840 |
| Fits | — |
OE supplier heritage. Backed by NGK’s long-standing original equipment standards.
Copper core design. Helps promote reliable ignition performance and durability.
Standard spark plug. A direct-fit replacement for routine ignition service.
Cross-references AMS Automotive 4000, AMS Automotive 4171 and Carlson 7840 for the same application. See all 11.
NGK CR5HSA Standard Spark Plug
The NGK CR5HSA standard spark plug is built for dependable ignition performance in a wide range of small-engine and powersports applications. As part of NGK’s Standard Spark Plug line, it uses a copper core center electrode, nickel tip materials, and a 5,000-ohm resistor to support stable spark delivery and reduced electrical noise.
Key Features
- Part number: CR5HSA / 7840
- Standard spark plug design for OE-style replacement service
- Copper core center electrode for consistent heat transfer
- Nickel center and ground electrode tip materials
- 5,000-ohm resistance for ignition system noise suppression
- Pre-gapped to .028 inch
- 10 mm thread diameter, 0.5 inch reach, flat seat
- 5/8 inch hex size with stud terminal
Product Details
NGK’s Standard Spark Plug line focuses on original-equipment-style construction and broad application coverage across automotive, motorcycle, marine, and small engine use. The CR5HSA spark plug follows that approach with a standard ground configuration, single ground electrode, and a manufacturer heat range of 5. For buyers searching for NGK CR5HSA spark plug replacement, 7840 spark plug, or a standard NGK ignition component, this plug provides the core specifications needed for routine tune-up service.
This part cross-references Carlson 7840 for the same application.
Common Issues This Spark Plug Can Address
- Hard starting caused by worn or fouled spark plugs
- Rough idle from weak or inconsistent spark output
- Misfire symptoms related to electrode wear
- Reduced throttle response from degraded ignition performance
- Electrical interference concerns in ignition circuits
Installation Notes and Tips
Verify the thread diameter, reach, seat type, and pre-gap before installation. Use the correct spark plug socket for the 5/8 inch hex, and confirm the terminal style matches the ignition lead or cap. For best results, compare the removed plug to the NGK CR5HSA / 7840 specifications before final tightening.
Compatible With applications that call for a CR5HSA-style spark plug, including select Honda motorcycle and small-engine service references where this NGK part number is specified. Fits should be confirmed by matching the vehicle or equipment service specification to the plug dimensions and heat range.
Quality Assurance
NGK is a long-established OE supplier with manufacturing and distribution operations supporting domestic and import vehicle applications across North America and global markets. The brand’s Standard Spark Plug line is built to original-equipment standards for durability and consistent operation.
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