breather pipe on 99 yz 125

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Sep 4, 2003
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#1
is there meant to be exhaust fumes coming out of the black breather coming out of the cylinder block? there is also a little oil dripping out of this. is this normal? what kind of oil is it(2 stroke or gear oil)? is it something to worry about? any info would be greatly appreciated. thanks
 
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Sep 6, 2003
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#2
The same thing was happening to my 01 YZ125. I posted the same question in another forum but no one had an anwser. My bike is running fine, so I guess it isn't much of a problem.

Slick
 

ACS

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Apr 17, 2001
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#3
Its a breather from the front of the powervalve area. It will drip a bit of burnt oil from the engine as they wear. Smoke is exhaust smoke and it means that the valves are leaking fairly badly, performance will be down. A 99 will be getting pretty tired now anyway. The only fix I know is a new barrel and exhaust valves(2 of them). There may be a small O ring on the valves shaft that can be replaced but I am not sure. Maybe check one of the online parts microfisch but getting the valves apart is a pain as they use a tiny allen bolt that always seems to freeze and destroys the key or bolt or both.
 

billtx

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Dec 22, 2002
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#4
I don't think smoke/oil coming out is a big deal. I have the same bike, just rebuilt the top end. Yamaha dealer helped me take apart the powervalve - they use Torx screws and are red loctited in from what I can tell. They saw nothing wrong.

The powervalves hang down at low RPM and divert some exhaust against the shaft that holds the valve and ultimately into the chamber that houses the linkage mechanism and vent hose. I've noticed smoke on other bikes, seems to be more on warm up then after.

Should be OK.
 

yz250flash

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#5
I have seen many brand new bikes do this. My brother's '03 YZ250 did it and both my YZ250 and YZ125 do it. It's nothing to worry about.