KTM 250 SX-F Spark Plug Replacement and tools

The stock 2013 KTM 250 SX-F Spark Plug is NGK LMAR9AI-8 spark plug.  It’s a slightly different spark plug than I use on my 2014 KTM 450 SX-F.  I replaced it with the same NGK laser iridium plug that I had already installed.

14mm Thin-Walled Socket

One specialized tool that you will need to get to the KTM 250 SX-F spark plug is a thin-walled 14mm socket.  It’s a tight fit and I found that a thin-walled socket is the only socket that can be used on my bike. I was the second owner of my 2013 KTM 250 SX-F and I didn’t get this with my bike.  I had to buy this socket and keep it in my KTM tool kit. This socket is extra useful on the KTM 250 SX-F spark plug because of the way the spark plug is accessed in the head.  

Tools

The other tools that are needed are a 3/8 in inch ratchet wrench, a 13mm 6 point shallow socket, and a 3 inch 3/8 extension. Another tool that I highly recommend is getting a bendable magnetic pickup. This has been one of the most useful tools that I’ve owned.  I use it almost every time I work on my bikes. With the limited spaces above the head on the KTM, this pickup is needed to lift the spark plug and the socket out of the spark plug tube. 

Tank Removal

To get access to the spark plug you’re going to have to remove the gas tank. The first step is removing the seat and fenders. The next is to remove the quick disconnect on the gas line.  Disconnect the fuel pump plug on the back of the tank. Last is to make sure that you remove the small bolt that connects the tank directly to the frame.

KTM 250 SX-F Spark Plug Boot

The spark plug boot is aligned directly under part of the frame. It’s a bit tricky to get out and it comes out on one side only. If you look at the bike from the top, the spark plug boot comes out on the right-hand side. It’s a tight fit but you can see that there’s a notch in the frame to give you a little room to pull the boot out.  In the third picture, you can see there is a notch in the small part of the frame right above the spark plug hole.

Spark Plug Removal Tools

In the next three pictures, you can see why you need the socket and socket extension to reach down to the spark plug. The spark plug hole is pretty deep and you can’t directly access it with just the spark plug socket tool from KTM. Additionally, directly above the spark plug tube is a part of the frame. Using the 3-inch extension will give you just enough room to loosen the spark plug without hitting the frame.

Spark Plug Removal

To remove the socket and the spark plug, it’s really convenient to have a bendable magnetic pickup. I said before, this is one of the tools I use all the time. The spark plug socket will slide out of the wrench and it will sit down in the spark plug tube. I found that using the magnetic pickup I could grab the socket and then after that the spark plug itself.

Old vs New Spark Plug

Here is the old NGK LMAR9AI-8 next to the new one. I’m not sure how many hours I put on it but the spark plug,  but it looks pretty good as far as I can tell.

KTM 250 SX-F Spark Plug Instal

Installing the spark plug is straightforward. The NGK LMAR9AI-8 doesn’t need to be gapped and can be installed straight from the box. Slide the spark plug down the spark plug tube with your finger so it doesn’t smash into the head. Reinsert the extension and spark plug socket and hand tighten it. Once it’s a hand tightened, use the wrench and give it a quarter turn more.

Gas Line Connector

After the spark plug is installed reconnect the spark plug boot and attach the gas tank and fenders. One area to be careful about is when you reconnect the gas line Quick Connect. Make sure that there is no dirt and that the O-ring hasn’t been damaged. Even a small piece of dust can end up clogging the fuel injector.