What Is The Purpose Of This?

Is there a reason why Yamaha put this small hole in the cylinder head? I was just wondering what it does, since I noticed water dripping out of there after I washed the bike and wondered if that was a bad thing or not.

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Is there a reason why Yamaha put this small hole in the cylinder head? I was just wondering what it does, since I noticed water dripping out of there after I washed the bike and wondered if that was a bad thing or not.

DSC_0051.jpg

EFI Duh! JK I have no idea, was wondering the same thing....

That is a whichahoozit valve. With out that, your four stoke would sound like a two smoker! Well, not really. That is a real good question! I will guess and say something to do with compression release.

not sure whats its real purpose is but if you shoot a little air in there it makes it real easy to pop the sparkplug boot off

If indeed it pops the plug boot off wouldn't it seem this is a drain hole for the cavity that the plug sits in?

If indeed it pops the plug boot off wouldn't it seem this is a drain hole for the cavity that the plug sits in?

That's exactly what it is and you should cover it up when washing our 250F or riding in wet/muddy conditions to prevent clogging it or getting dirt up there. It's all in your owners manual...............read it sometime. :applause:

That's exactly what it is and you should cover it up when washing our 250F or riding in wet/muddy conditions to prevent clogging it or getting dirt up there. It's all in your owners manual...............read it sometime. :D

AGREED NYMXer! :prof:

very very important to stick a golf tee 0r equivilent in this hole when washing - otherwise the sparkplug will rust from dirt and water over time - which is no big deal until you remove the sparkplug and all that crap falls into the cylinder....not good....

I always spray contact cleaner from the top after removing sparkplug wire to remove as much debree as possible....

Oh yea....one more thing, remove that golf tee ASAP after rinsing as it will swell up and be very difficult to remove later :applause:

That hole is the drain for the area around the spark plug. Either from washing or from water when riding. It is best to check that it is free from debri so it does drain and not let water build up around the plug.

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