Strange hole in engine my new yz450f...

hey all...

Went to break in my new yz450f today...glen helen was hosting a race so I went to perris raceway, didnt like it much..pretty small so we backtracked and pulled of the feeway in Rubedoux to a little spot with a BUNCH of hills...STEEP / HIGH hills so I figured that I could load the rings and still not over rev tooooo much...anyway got home tonight and was just kinda lookin at the bike and noticed a hole on the right (kick starter) side of the is threaded for what I would guess would be a 6mm I looked in the manual and there is no verbage about it but it is in a few schematics and it seems to lead off of/into (depending on perspective) the spark plug... it is centered between the cylinder studs and a bit higher up. What is this hole? Should there be a bolt in it?

Thanks all!!!

Oh a two stroke rider who has`NEVER been on a bike like this I can say that I am hooked...the torque`is just completely insane and the hook up is very sweet. The sweet spot is the complete PB. And to think I used to think it was just a phase...


It sounds like you're describing the weep/drain hole for the plug ... It's fine as is ...

If you mean the hole that can be seen right above the "bomb" in my header in this pic, it is a drain hole for the spark plug so if water gets in your sparkplug hole it will not stay there and corrode the plug too badly.




Man, I could not find one word in the manual about it...

Is there any mention of it in the manual?

Thanks again everyone!


When you wash your bike, plug the hole with a golf tee.

it can also be used to blow compressed air up and around the spark plug to clean out any debris before removing the plug, once the cap is removed from the spark plug of course

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