2009 YZ250F Leaking out of hole in cylinder. Please help

4 replies to this topic
  • Ashman_46

Posted January 18, 2013 - 03:52 AM


Hi guys. Today I was riding my 2009 yz250f around some trails and on the beach. After about 1/2 an hour there was a small amount of sticky/tacky yellow liquid leaking out of the small hole in the cylinder. In the attached photo the hole is shown towards the bottom left corner of the photo in the center of the cylinder. I assume it is right where the valves are, what could be leaking out of there? I have searched on the internet but couldn't find anything about it. Has anyone else had this or know of this? Or even just has any info on what this hole actually is? Thanks
yz250f engine.jpg

  • numbhands

Posted January 18, 2013 - 04:36 AM


I think thats the drain hole for the spark plug tunnel? Its there to allow any water that finds its way into the plug area to drain away. If the rocker cover gasket is leaking in that area, any oil collecting there would drain out too. have a look down the plug hole and see if its oily in there...

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • kx450f63

Posted January 18, 2013 - 05:48 AM


Yes, that is a weep whole for the spark plug tube. The tube is sealed by o-rings. Chances are you have an o-ring leaking. If you pull the valve cover off you will see how it functions.

  • grayracer513

Posted January 18, 2013 - 08:04 AM


That is the spark plug well drain, but the well is sealed only by the plug boot/coil seal on top (which is not your problem) and by the cam cover gasket, which is the likely culprit. No O-rings.

A second, much simpler possible cause, even though less likely, is a loose spark plug.

  • Ashman_46

Posted January 20, 2013 - 08:23 PM


Alright thanks guys, Ill check if the spark plug is tight and if there is anything in the tube. Nothing has leaked out since so hopefully isn't a big issue. Might take the rocker cover off if I have to.

Related Content


BIGBORE FOR YZ450F 2006? by Taattie94

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  30 replies

1998 yz400f will not idle. by trolley

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  32 replies

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.