What is this hole and how do I plug it?

[garyweliver]

I have a hole in the head where it looks like a freeze plug goes(lower right circle), but I'm not sure. Water leaks out of here when it is sitting, I had not noticed this before. It measure 4.3mm and there is a similar looking plug where the oil line connects to the back of cylinder(upper right circle).

Where can I buy a plug, Yamaha does not show this on their Parts website and my Yamaha service manual does not address this either.

Thanks

[SPLATT]

The lower one is for water to drain from around the spark plug as for the other one I would have to go look at mine to give you an answer.

Steve

[KennyMc]

What year is your bike. My '07 WR450 only has the one that you circled in the middle. It looks like where the other one is on my bike it is part of the casting.

[garyweliver]

It's a 1999. The plug on the LEFT has a little plug, like a freeze plug, the one on the right I can insert a small wire that goes into the head and water is seeping out of here,

[garyweliver]

Why would water need to drain from around the spark plug? Does your hole have a plug in it?

[Frostbite]

Why would water need to drain from around the spark plug? Does your hole have a plug in it?

The spark plug sits deep in a hole that goes through the valve cover and into the cylinder head. If water stayed in the hole then your spark would short to ground, like when a bike gets wet. this hole is a drain from the base of the sparkplug to allow any buildup to drain out. The stock plug cap fits pretty snugly into the valve cover, so it's not like there's water flooding in there, but some will get in, and some condensation.

The other hole near your oil line is where the factory drilled the oil passage through the head from the outside (because the hole had to turn 90 degrees), and then plugged the outside with the ball. Are you sure water is leaking out of that hole? If anything is leaking out of there it should be oil, unless you have a bad head gasket. Then coolant may be leaking down to the base of the sparkplug and leaking out that hole, and coolant may be mixing with your engine oil and leaking out the top hole. Check your oil to see if there's any coolant in it, and if not, double check to see what's coming out the top left hole. Draining out the bottom hole is normal and good - don't plug that hole!

[WR_Dave]

I would make sure the spark plug boot is down snug or that the O-ring is not gone, you are probably getting water into the spark plug area when washing the bike. That hole is for the reason Frostbite gave , to keep water from filling up the spark plug recess and shorting out the spark. Is your coolant low and is it coolant or just water?? WR Dave

[garyweliver]

Thanks, Good information. I do not have anything coming out the hole by the oil line (left circle) I just used it as an example of a similar looking hole that had a plug, and the hole seeping water out looks similar but doesn't have a plug, suggesting in my mind that something possibly could have lost out.

My coolant right now is empty. There's just what is left in the engine, which has anti-freeze in it.

[Frostbite]

Thanks, Good information. I do not have anything coming out the hole by the oil line (left circle) I just used it as an example of a similar looking hole that had a plug, and the hole seeping water out looks similar but doesn't have a plug, suggesting in my mind that something possibly could have lost out.

My coolant right now is empty. There's just what is left in the engine, which has anti-freeze in it.

Kool. I just re-read your first post and saw that you didn't mention a leak at the top hole.

So all is good.

Cheers

Frosty

[brad the best]

i put grease on the coil-over were it mates with the valve cover , keeps the crap out .

[matt4x4]

Just a little note because everyone seems to forget about that lower hole - yes, it's a drain for water if it gets in, but just as important, maybe even more so, you're supposed to blow air up/into it BEFORE you ever take your spark plug out, if dirt ever gets down in there and you take your plug out - the dirt will immediately fall into your cylinder - not a good scenario.

[Island Boy]

The lower hole should only be plugged when you wash / spray down your bike to prevent unnecessary water entering the cylinder head. I use a golf tee, it works great. Just dont forget to remove it when you are done.