Servicing the Spark Plug on a 2004 KLR-650

Warning

I am not a mechanic or a representative of any motorcycle or tool manufacturer or anything else official. This page is only my notes on doing this procedure myself. Although I believe what I have documented here is correct, I make no promises and you do this at your own risk.

Objective

Servicing your spark plug is part of the regular service schedule for your bike. At the specified intervals, you should clean or replace it, and check the spark gap size.

Required

Tools

• Rear stand (recommended)
• Phillips screwdrivers
• Hex wrenches
• Metric sockets
• Spark plug socket (the one from the bike tool kit will do)
• Torque wrench
• Spark plug gap gauge or feeler gauge

Supplies

• New spark plug or cleaning equipment

Difficulties & Warnings

Some difficulties could be:

• Over-tightening when re-installing the plug. Use a torque wrench.
• Cross-threading when re-installing the plug.
• Breaking the plug by trying to use a regular (non-spark-plug) socket.

Procedure

Putting the bike on a rear stand makes this job much easier by levelling the bike and holding it steady.

First you must

1. Remove the seat
2. Remove the gas tank

Then:

With the gas tank removed, stand on the right side of the bike where you can clearly see and reach the top of the engine.

Looking down into the recess on top of the engine, we can see the spark plug coil (large wire) and the temperature sensor (small wire).

Disconnect the spark plug wire by pulling it sharply upward.

Now you can see the white porcelin top of the spark plug.

Advice added from a commenter “Z” (thanks): Before the next step, use compressed air to blow away any grit or debris sitting on the engine cover near the spark plug. Otherwise, when you remove the plug, this may fall into the cylinder.

Use a suitable socket to remove the spark plug. It needs to be a deep 18mm socket, ideally with a rubber internal brace to support the spark plug body. The spark plug socket in the bike’s tool kit, shown here, will work. It needs to be turned with a 17mm wrench.

Lift the plug out, still in the socket, then free it from the socket.

Here is the used, dirty, spark plug.

Replace it with a new one (part number from your manual), or clean the existing plug if it is otherwise undamaged.

If you do this often, or have more than one small engine in your life, and have compressed air, it is worth buying an air-powered spark plug cleaner. I found one for about $20 on eBay.

This is the same plug, cleaned in the cleaner, which works like a small sand-blaster with a fine grit.

Use a feeler gauge to check the gap in the electrode. My manual calls for 0.2 to 0.25 mm gap, and the plug was in-spec. If the gap is not in spec but is close, gently adjust it by bending the electrode.

Replace the spark plug, being very careful that it goes in straight. Finger-turn it several turns to ensure it is not cross-threaded, then tighten it. Ideally, use a torque wrench to avoid over-tightening.  My manual specifies 14 Newton-Metres10.3 foot-pounds torque.

Re-install the spark plug wire by pushing the coil down firmly onto the spark plug.