Replacing Spark Plugs

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Remove and Install Ignition Coils

A - Cap Screw

B - Ignition Coil

C - Connector

1. CAUTION: Electrical shock may occur if you contact live electrical components. Disconnect power before servicing ignition system.

   NOTE: Replace spark plugs every 50,000 miles, regardless of months of operation. Also, replace spark plug boots every other spark plug change or every 100,000 miles.

   Disconnect ignition coil electrical connector (C).

2. IMPORTANT: Avoid damage to spark plug boot or ignition coil. Pull ignition coil straight out when removing.

   Loosen cap screw (A) and remove ignition coil (B).

3. 
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   Remove Spark Plug Boot

   A - Spark Plug Boot

   Remove spark plug boot (A), using JDG815 Spark Plug Boot Pliers if necessary.

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4. Check plug bore for water or debris. If present, use compressed air to remove debris. Replace plug boot if necessary.

5. 
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   Remove Spark Plug

   B - Spark Plug

   Remove and discard spark plug (B).

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6. 
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   Spark Plug Gap

   A - Spark Plug Gap

   Adjust gap (A) on new spark plugs to specifications.

   Item	Measurement	Specification
   Spark Plug	Gap	0.38 mm (0.015 in.)

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7. IMPORTANT: Platinum spark plugs are used to attain maximum plug life. John Deere Part Number RE51610 (marked RC78PYP) MUST BE used.

   
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   Install Spark Plugs

   Install spark plug and tighten to specification below.

   Item	Measurement	Specification
   Spark Plugs	Torque	38 N˙m (28 lb-ft)

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8. Apply silicon dielectric grease to spark plug terminal and spark plug boot.

9. Install spark plug boot.

10. 
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    Remove and Install Ignition Coils

    A - Cap Screw

    B - Ignition Coil

    C - Connector

    Apply LOCTITE® 242 Thread Lock and Sealer to threads of coil-to-bracket cap screws (A).

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11. Apply a small drop of dielectric grease to metal terminal of plug and coil terminal.

12. Install coil (B) and tighten cap screws.

13. Connect electrical connector (C) to coil.