Help!! changing plugs.

I know I saw a post sometime back about changing the plug in a WR400 but I can't find it. I'm a newbie at working on the WR thumpers and now my plug is fouled and I can't get the darn thing out. Do you guys use a special socket or what? Thanks!!

You need the socket that came in the tool kit. It's articulated in the middle so you can clear the frame tube.


I wish I had the tool kit! I guess I will have to go to the local dealer and order one.

If you have a regular 3/8" drive ratchet set, you can simply use the 5/8" spark plug socket with the articulated (U-joint) socket extension.

It never hurts to putr a little never seize lubricant on those plug threads when you install that new plug. It will assure that it comes out easily next time and protect those threads in that expensive head.

Don't overtighten the plug when installing it also.

I just changed my plug and noticed rust around the metal portion that the wrench slides over. Anyone else have this problem? I guess it's water from washing the bike that is getting down in the hole.

I noticed it last time and assumed I didn't get the plug wire cap down far enough onto the plug so that it would seal agains the valve cover. Same thing this time though.


I also noticed the rust on my plug- I don't think it had been changed by the previous owner for quite some time. I've heard that you can spray some WD 40 down into the hole after cleaning to chase the water out the drain hole on the side of the cylinder.

I also don't have the stock plug wrench, and the 5/8" socket tool and U-joint seem to be hard to use. Does anybody know the Yamaha part number for the toolkit wrench?

stock plug wrench: 5BE-2814F-00-00

Thanks sabin! :)

i think rust on your plug is from water entering through the (ironically named) drain hole in the side of the head. i was advised to tape it over whenever you clean your bike, as if you get enough water in there then get your motor hot you can boil the water in there and blow the plug cap off.



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