Hole in engine

[Thumpologist]

What is that hole in the right hand side of the engine half way between the head bolts and just a little below?? I can't seem to find any reference to it in the manual.

[YZ400Court]

Spark plug drain hole??

[gal]

yes, im sure that's what he meant....

[Boit]

Yes, that hole allows any moisture to drain out of the space around the spark plug. If it was not there, pressure would build from the heat and push the spark plug lead off. Plus, this hole is handy for blowing debris from the spark plug before you change it. Just remove the lead and use compressed air and shoot it thru that hole and watch all the trash that comes flying up. Protect your eyes. You can also use a shot of air to push the plug lead up about an inch so that you can get a grip on it for removal. I'm beginning to get a bit of arthritis in my fingers and can't use them like I once could, so any help is a good thing.

[Thumpologist]

Thanks for the tips. That hole is a great feature. I have not had to change my plug yet.