NGK 6630 UR4 Spark Plug, Replaces Cushman 830931 and John Deere AM38027, Fits Kohler Engines

The NGK 6630 is a standard nickel spark plug built on NGK's proven OE plating and design, offering reliable ignition performance for small gas engines. The plug carries a corrosion-resistant plating that keeps installation and removal easy over the plug's service life, while the solid copper core delivers strong heat dissipation, conductivity, and a broad heat range so the engine keeps firing cleanly across varying loads and speeds. NGK Standard plugs like the 6630 are an OE cornerstone, and this design has provided decades of dependable use in small engines.

This plug uses a semi-surface discharge ground configuration with a nickel ground electrode and a nickel center electrode tip over a copper core, and it carries a 5,000 ohm resistor for suppression. The hex size is 5/8 inch, matching standard small-engine spark plug sockets. It is a direct fit and cross-reference match for a range of Kohler small gas engines, and it replaces several OEM part numbers from other engine manufacturers. Always check your engine and maintenance manual to confirm this is the correct plug and gap for your equipment, since using the wrong plug can reduce performance, cut fuel economy, or damage the engine.

Specifications

• Brand: NGK
• Manufacturer Part Number: 6630
• Spark Plug Type: UR4
• Resistance: 5,000 ohms
• Ground Configuration: Semi-Surface Discharge
• Ground Electrode Core Material: Nickel
• Center Electrode Core Material: Copper
• Center Electrode Tip Material: Nickel
• Hex Size: 5/8 inch
• Weight: 0.15 pounds
• UPC: 087295166307
• OEM Cross-Reference: Cushman 830931, John Deere AM38027, ACDelco 41-905, ACDelco CR 45 TS

Fitment

• Kohler gas engines: 17.0/KT17, 19.0/KT19, 21.0/KT21, 16.0/MV16, 18.0/M18, MV18, 20.0/M20, MV20, OHC

Replaces (OEM)

• Cushman 830931
• John Deere AM38027
• ACDelco 41-905
• ACDelco CR 45 TS

Frequently Asked Questions

What is the part number for this spark plug? The manufacturer part number is 6630, corresponding to the NGK UR4 standard spark plug design.

Does this plug replace a Cushman or John Deere spark plug? Yes, the NGK 6630 UR4 spark plug is a direct cross-reference replacement for Cushman 830931 and John Deere AM38027.

Is this plug compatible with ACDelco part numbers? The NGK 6630 UR4 cross-references to ACDelco 41-905 and ACDelco CR 45 TS, so it can be used in place of either of those ACDelco spark plugs.

What hex size wrench does this spark plug need? The NGK 6630 UR4 has a 5/8 inch hex size, which matches standard spark plug sockets of that size.

What is the electrical resistance of this spark plug? This plug carries a 5,000 ohm resistor, built into the NGK 6630 UR4 for radio-frequency suppression.

What materials are the electrodes made from? The NGK 6630 UR4 has a nickel ground electrode and a nickel center electrode tip, with a copper center electrode core for heat dissipation.

Which Kohler engines does this spark plug fit? The 6630 fits Kohler gas engines 17.0/KT17, 19.0/KT19, 21.0/KT21, 16.0/MV16, 18.0/M18, MV18, 20.0/M20, MV20, and OHC models.

How much does this spark plug weigh? The NGK 6630 UR4 spark plug weighs 0.15 pounds.

Is this a genuine NGK spark plug or an aftermarket copy? This is a genuine NGK-manufactured plug, listed under NGK part number 6630 (UR4 type), not a third-party copy.

What ground electrode configuration does this plug use? The 6630 uses a semi-surface discharge ground configuration, which differs from the standard ground design used on some other NGK plug types.

Do I need anti-seize compound when installing this plug? NGK does not list this standard nickel-plated 6630 UR4 plug as trivalent-plated anti-seize-free, so follow your engine manual's anti-seize recommendation for installation.

How do I know if the 6630 is the right plug for my engine? Check your engine and maintenance manual before installing the NGK 6630 UR4, since using the wrong spark plug can reduce performance, lower fuel economy, or damage the engine.