Hole in right side of cylinder head...what is it?..its spitting oil??

K...just replace my cylinder head gasket on 2000 WR400, and the valves were checked/inspected/serviced at a yamaha dealer. There is a small hole on the right side of the cylinder head and it is spitting oil out, especially when you hit the throttle.... it never did this before??? :):D

The hole is located on the lower portion of the cylinder head (about 1 inch up at lower/upper cylinder interface) between the outer 150 mm cylinder head bolts. See page 2-19 of your manual.

Is it an over flow..pressure realease "device"? Was there a ball bearing in there and it blew out??

Or did the gasket just not seal properly and it is causing me problems?...I torqed it properly and in stages . Bike runs well, lots of juice and sounds burly.

Thx for your help

Pop your valve cover off.

It is spitting oil out of the spark plug water drain hole.

This is not good.

Ascertain the cause asap.

Maybe just the spark plug is loose :).

Smoke :D

It is a bit like blood coming out your nose... shouldn't happen and you need to check why... I would suggest that your valve cover gasket is not seating properly, or is damaged, and the sparkplug cavity drain hole is the only way out for the oil that is leaking past... take the valve cover off, inspect the rubber gasket, and then replace if damaged or reinstall carefully. Your problem should go away then...

Also, when you hit the throttle, both the engine oil pressure and volume to the valve area is increased, as well as the crankcase pressure, so it will blow out more and faster... check your breather hose is not kinked/blocked either...

Good luck,


That is the spark plug drain hole should not have oil coming out of it FIX QUICK. :D:)

You guys keep fallin for this guys posts! I called him a troll on his first post and I see he is at it again on his second! :)

There's a hole in my head where the rain comes in and stop my mind from wandering ...

Beatles :)

Its a water drain for the spark plug well. You may have a leaking valve cover, this would mean you have a plug submerged in oil.

You guys keep fallin for this guys posts! I called him a troll on his first post and I see he is at it again on his second! :)

We had this happen on our race bike, BTW, oil out the weep hole and there was some midnight oil burned to get everything straightened out before our first national and first podium...

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