573935702 Ignition Coil

Key Features

• High-Energy Spark Output: Precision-wound internal coils generate a consistent, high-voltage spark to ensure reliable ignition even in cold weather or high-altitude conditions.
• Optimized Ignition Timing: Factory-set electronic timing provides efficient combustion across the entire RPM range, improving throttle response and fuel economy.
• Weather-Sealed Encapsulation: The internal electronics are fully potted in high-grade epoxy to protect against moisture, vibration, and the high heat typical of heavy-duty chainsaw operation.
• Durable Spark Plug Boot: Equipped with a heavy-duty silicone boot and a high-tension lead designed to resist cracking and "arching" (leaking electricity to the engine block).
• Direct Bolt-On Installation: Engineered to the exact mounting specifications of the original Husqvarna module, ensuring the correct "air gap" between the coil and the flywheel.

Replaces / Cross-Reference Part Numbers

• 573 93 57-01
• 573 93 57-02
• 544 04 70-01
• 582 86 89-01
• 522 96 71-01

Compatibility & Fitment

This ignition coil fits the second-generation "X-Torq" engines used in Husqvarna and Jonsered mid-range chainsaws. Key compatible models include:

• Husqvarna: 435, 435E, 440, 440E, 445, 445E, 450, 450E (and II models).
• Jonsered: CS2240, CS2240S, CS2245, CS2245S, CS2250, CS2250S.
• McCulloch: CS410, CS450.
• Note: Always check your original coil's part number; early 435/440 models may use a different module with a different plug wire angle.

When to Replace

• No Spark: The most obvious sign; after checking that the spark plug and kill switch are functional, the engine still lacks ignition.
• Engine Cuts Out When Hot: The saw starts and runs fine for 10–15 minutes, but dies as the engine heats up and won't restart until it cools down (a classic sign of internal coil failure).
• Engine Misfires: Rhythmic "popping" or stuttering at high RPMs, indicating the coil is failing to provide a consistent spark under load.
• Hard Starting: A weak spark requires excessive pulling and perfect fuel conditions just to get the engine to fire.
• Visible Damage: The spark plug wire is frayed, or the epoxy housing on the coil has cracked or melted.

Installation & Timing Tips

• The Business Card Trick: For the engine to run correctly, the "Air Gap" between the coil legs and the flywheel magnets must be precise. A standard business card (~0.010" to 0.012") is the perfect gauge. Place the card between the coil and flywheel, let the magnets pull the coil tight against it, then tighten the mounting bolts.
• Check the Ground: Ensure the metal mounting "legs" of the coil and the engine block are clean and free of rust or oil. The coil grounds through the mounting bolts; a poor ground will cause weak or no spark.
• Kill Switch Wire: Be careful when reconnecting the small spade terminal for the kill switch. If this wire is pinched or grounded against the engine block, the saw will never start.
• Inspect the Flywheel: While the cover is off, check the magnets on the flywheel for metal shavings or debris. Use a rag to clean them to ensure the strongest possible magnetic pulse.
• Spark Plug Health: Always install a fresh NGK BPMR7A (or equivalent) spark plug when replacing the coil. A fouled or improperly gapped plug can put undue stress on a new ignition module.