Spark Plug Tool

I just bought a used 1998 WR400. The bike appears to be bone stock and came with the factory owners/repair manual.

Today I started my journey into the amazing black hole that swallowed the spark plug. :D I am amazed at the effort required to change the plug and hope that I never have to do it on the trail.

Unfortunately, now that I have made this post it will happen soon. I removed the rad covers, seat and tank. Pushed aside the misc wires and the throttle cables, and lo and behold there was the plug wire. Three trips to the tool box later and 15 minutes later I changed my first plug. :D

What a frigging nightmear! Is there a specific tool(s) that make this job easier?

Where there tools that came with the bike new that I should go and find?

Oh by the way, still won't start! Hope it's only due to the cold here in Michigan :)

i use a 5/8ths deep well socket, universal on that, and my ratchet. nothing fancy. use a piece of fuel line to spin the plug and remove it. it's a pain but you won't have to change it often. the stock tool is a universal type set up. try not to shoot water into the little hole on the side of the head. it's a drain for the spark plug area. they get rusty and you don't want that in your motor.

You can make it a little easier on yourself if you leave the radiator shrouds on the tank, then you just have 6 bolts and the stretchy rubber thing to do...

You may want to use a universal or a wobble extension on the plug socket, or a longer extension to get above the frame...

A tip for installing the plug... use a 4-6" piece of fuel hose to start to plug in it's hole... if it is going to crossthread, the hose will slip on the plug and save you that heartache...

Try an iridium plug as well, I like them, can't quantify why, just do...

Use some compressed air to blow the crud out before you pull the plug... and add a squirt of WD40 after you install the plug, and then, by using a golf tee to block the drain hole, you should stay nice and dry (and rust free) in there when washing the bike...

Good luck,


And torque the plug to the right spec's. :)

I bought a MotionPro tool speific for the Yamaha that has a few nice features that makes the process much easier. It is about $20.

Unfortunately, the easiest way is to use the stock spark plug tool that came with the bike and turn the top of it with a wrench. This can be done without removing anything and it can be easily done on the trail. I am sure you can get the OEM tool from Yamaha. I would bet it is under $20 and in my opinion worth it. :)

Bought one here for US$5 OEM

I paid $8 for the OEM tool... it's easy to use and idiot proof (until someone builds a better idiot). :)

I bought a used WR426 and have been doing preventative maintenance. I tried to change the spark plug and couldn’t get the socket to get a grip. I then called the Yamaha Dealer and they sold me a Motion Pro socket. I tried that and that didn’t work either. Could the preveous owner have used some screwy plug in it and I have the wrong size socket? I also wonder if I have some junk or dirt that is blocking the socket. Any advice?

I will look into the tool from the dealer to make my life easier (who doesn't need that :)), but I went out and looked at the bike again and there is no way that I can see for the plug to be removed without removing the fuel tank.

Maybe the tank and plastic is different from the 400 to the 426?

yes the tank is different between a WR and YZ. The latter is smaller. Despite that I can/have changed my plug without removing the tank. Takes some patience but can be done.

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