Autolite 4051 Spark Plug

Autolite 4051 Copper Spark Plug

Autolite 4051 is a copper non-resistor spark plug built for quick starts, smooth acceleration, and improved fuel economy. It uses OE-style form, fit, and function, making it a direct replacement choice for a wide range of powersports and small-engine applications.

Key Features

• Copper center electrode for reliable ignition response
• Non-resistor design for applications that specify a non-resistor plug
• Nickel ground and center electrode tip materials
• Preset 0.025 in. gap with a flat seat design
• Short ceramic insulator and removable nut terminal
• 14 mm thread diameter, 0.750 in. reach, 13/16 in. hex

Detailed Description

The Autolite 4051 spark plug is engineered around a copper core and nickel electrode construction to support consistent spark delivery in demanding two-stroke and small-displacement engines. This part number 4051 is listed across a broad range of Kawasaki, Yamaha, Suzuki, KTM, Polaris, Honda, Arctic Cat, Ski-Doo, and John Deere applications, including models such as the Kawasaki KX65, Yamaha YZ85, and Suzuki RM85. For buyers searching for a copper spark plug for Kawasaki KX65, Yamaha YZ85 spark plug replacement, or Suzuki RM85 ignition service, this plug matches the specified fitment and gap requirements shown in the catalog data.

Autolite positions the Copper Non-Resistor Spark Plug line as an OE-style replacement option with form, fit, and function aligned to original specifications. Part number 4051 is also cross-referenced to Monroe Shocks & Struts 172286 and 182286 for the same application.

What It Is Used For

• Hard starting caused by worn or fouled spark plugs
• Rough idle or inconsistent combustion
• Loss of throttle response during acceleration
• Maintenance replacement for engines calling for a non-resistor copper plug
• Restoring correct spark gap and ignition performance

Installation Notes and Tips

Verify the engine-specific gap listed in the fitment notes before installation. The catalog data shows different preset or recommended gaps by application, including 0.018, 0.020, 0.024, 0.028, 0.030, and 0.032 inch specifications. Confirm thread diameter, reach, seat type, and terminal style against the removed plug or service manual. This part number 4051 is used in many two-stroke powersports engines, so matching the exact application is important.

Quality Assurance

Autolite supplies spark plugs to the automotive aftermarket and original equipment manufacturers and is a long-standing ignition product supplier. The 4051 follows OE-style construction and application-specific fitment data for dependable service.